Resistor ratios

G

George Herold

Guest
Hi all, I'm making this current output in fixed ratio's... 1,2,4... etc.
I'm using 0.1% RG series from susumu.
There are lots of 1:2 ratio's,
But the only 1:2:4 that I find (in stock at DK)
is 75/150/300. are there any others?

(There is 140/280/560, but 280 is a non-stock item at DK.)

75/150/300 also has 1.2K so a 1:2:4..16 ratio, which look nice.

George H.
 
On Monday, February 29, 2016 at 8:52:32 AM UTC-8, George Herold wrote:
Hi all, I'm making this current output in fixed ratio's... 1,2,4... etc.
I'm using 0.1% RG series from susumu.
There are lots of 1:2 ratio's,
But the only 1:2:4 that I find (in stock at DK)
is 75/150/300. are there any others?
Click to expand...

If it comes to it, just pick a stock value, and do two-in-parallel, one, two-in-series.
 
On Mon, 29 Feb 2016 08:52:23 -0800, George Herold wrote:

Hi all, I'm making this current output in fixed ratio's... 1,2,4... etc.
I'm using 0.1% RG series from susumu.
There are lots of 1:2 ratio's,
But the only 1:2:4 that I find (in stock at DK)
is 75/150/300. are there any others?

(There is 140/280/560, but 280 is a non-stock item at DK.)

75/150/300 also has 1.2K so a 1:2:4..16 ratio, which look nice.

George H.
Click to expand...

You don't say if you're using the resistors to program a current source
or what, but if you're willing to make an R-2R ladder you can get
1,2,4,8, etc., ad infinitum.

For that matter, you can make a DAC -- but you'd need good resistors.

--

Tim Wescott
Wescott Design Services
http://www.wescottdesign.com
 
On 02/29/2016 11:52 AM, George Herold wrote:
Hi all, I'm making this current output in fixed ratio's... 1,2,4... etc.
I'm using 0.1% RG series from susumu.
There are lots of 1:2 ratio's,
But the only 1:2:4 that I find (in stock at DK)
is 75/150/300. are there any others?

(There is 140/280/560, but 280 is a non-stock item at DK.)

75/150/300 also has 1.2K so a 1:2:4..16 ratio, which look nice.

George H.
Click to expand...
Well, 249/499/1000/2000 is close, and
255/510/1020 is nominally exact. (Susumu sells the E24 values in their
precision series as well, iirc.)

Cheers

Phil Hobbs

--
Dr Philip C D Hobbs
Principal Consultant
ElectroOptical Innovations LLC
Optics, Electro-optics, Photonics, Analog Electronics

160 North State Road #203
Briarcliff Manor NY 10510

hobbs at electrooptical dot net
http://electrooptical.net
 
On Monday, February 29, 2016 at 2:12:40 PM UTC-5, Phil Hobbs wrote:
On 02/29/2016 11:52 AM, George Herold wrote:
Hi all, I'm making this current output in fixed ratio's... 1,2,4... etc.
I'm using 0.1% RG series from susumu.
There are lots of 1:2 ratio's,
But the only 1:2:4 that I find (in stock at DK)
is 75/150/300. are there any others?

(There is 140/280/560, but 280 is a non-stock item at DK.)

75/150/300 also has 1.2K so a 1:2:4..16 ratio, which look nice.

George H.

Well, 249/499/1000/2000 is close, and
255/510/1020 is nominally exact. (Susumu sells the E24 values in their
precision series as well, iirc.)

Cheers

Phil Hobbs

--
Dr Philip C D Hobbs
Principal Consultant
ElectroOptical Innovations LLC
Optics, Electro-optics, Photonics, Analog Electronics

160 North State Road #203
Briarcliff Manor NY 10510

hobbs at electrooptical dot net
http://electrooptical.net
Click to expand...

Tim, Phil, thanks. I had a total brain fart today.
It's an opamp -> fet -> load/resistor_feedback
current source.
I wanted to switch R (with rotary switch) and I thought
I could do it in shunt/ parallel, until I tried to lay it
out.. oops. (I hope the odor did not escape my room.)

Max current is in the 200mA range. (limited by switch...)
Now I'm thinking about ditching the rotary switch and
using a latching relays.. ~$2-3 each (in 100)
Seems like I could do a lot with 3-4.
I'd still have to have inputs.. push buttons I guess..
and led indicators. A front panel pcb...
(rotary switches are on the shelf.)

Sorry for thinking out loud.

George H .

PS,
Phil, Re: 249,499, 1k, 2k, 4.02k
I wish we could "bend the log a bit"
and have 250,500,1k,2k,4k..

GH
 
On Monday, February 29, 2016 at 8:31:25 PM UTC-5, John Larkin wrote:
On Mon, 29 Feb 2016 16:49:53 -0800 (PST), George Herold
gherold@teachspin.com> wrote:

On Monday, February 29, 2016 at 2:12:40 PM UTC-5, Phil Hobbs wrote:
On 02/29/2016 11:52 AM, George Herold wrote:
Hi all, I'm making this current output in fixed ratio's... 1,2,4... etc.
I'm using 0.1% RG series from susumu.
There are lots of 1:2 ratio's,
But the only 1:2:4 that I find (in stock at DK)
is 75/150/300. are there any others?

(There is 140/280/560, but 280 is a non-stock item at DK.)

75/150/300 also has 1.2K so a 1:2:4..16 ratio, which look nice.

George H.

Well, 249/499/1000/2000 is close, and
255/510/1020 is nominally exact. (Susumu sells the E24 values in their
precision series as well, iirc.)

Cheers

Phil Hobbs

--
Dr Philip C D Hobbs
Principal Consultant
ElectroOptical Innovations LLC
Optics, Electro-optics, Photonics, Analog Electronics

160 North State Road #203
Briarcliff Manor NY 10510

hobbs at electrooptical dot net
http://electrooptical.net

Tim, Phil, thanks. I had a total brain fart today.
It's an opamp -> fet -> load/resistor_feedback
current source.
I wanted to switch R (with rotary switch) and I thought
I could do it in shunt/ parallel, until I tried to lay it
out.. oops. (I hope the odor did not escape my room.)

Max current is in the 200mA range. (limited by switch...)
Now I'm thinking about ditching the rotary switch and
using a latching relays.. ~$2-3 each (in 100)
Seems like I could do a lot with 3-4.
I'd still have to have inputs.. push buttons I guess..
and led indicators. A front panel pcb...
(rotary switches are on the shelf.)

Sorry for thinking out loud.

George H .

PS,
Phil, Re: 249,499, 1k, 2k, 4.02k
I wish we could "bend the log a bit"
and have 250,500,1k,2k,4k..

GH




Can you do the current control on the input side, rather than
switching 200 mA? Use an analog mux or a low-current rotary switch.
Click to expand...

Yeah it would be much better to do most of the switching
at the front end.... I need less than 2 decades.
(And I'm feeling like someone will want more current.)

Thanks.. I was stuck looking at wrong thing.

George H.


Does anybody still make R-2R ladder networks? I guess you could make
your own.

Use a DAC?



--

John Larkin Highland Technology, Inc
picosecond timing precision measurement

jlarkin att highlandtechnology dott com
http://www.highlandtechnology.com
Click to expand...
 
On Mon, 29 Feb 2016 16:49:53 -0800 (PST), George Herold
<gherold@teachspin.com> wrote:

On Monday, February 29, 2016 at 2:12:40 PM UTC-5, Phil Hobbs wrote:
On 02/29/2016 11:52 AM, George Herold wrote:
Hi all, I'm making this current output in fixed ratio's... 1,2,4... etc.
I'm using 0.1% RG series from susumu.
There are lots of 1:2 ratio's,
But the only 1:2:4 that I find (in stock at DK)
is 75/150/300. are there any others?

(There is 140/280/560, but 280 is a non-stock item at DK.)

75/150/300 also has 1.2K so a 1:2:4..16 ratio, which look nice.

George H.

Well, 249/499/1000/2000 is close, and
255/510/1020 is nominally exact. (Susumu sells the E24 values in their
precision series as well, iirc.)

Cheers

Phil Hobbs

--
Dr Philip C D Hobbs
Principal Consultant
ElectroOptical Innovations LLC
Optics, Electro-optics, Photonics, Analog Electronics

160 North State Road #203
Briarcliff Manor NY 10510

hobbs at electrooptical dot net
http://electrooptical.net

Tim, Phil, thanks. I had a total brain fart today.
It's an opamp -> fet -> load/resistor_feedback
current source.
I wanted to switch R (with rotary switch) and I thought
I could do it in shunt/ parallel, until I tried to lay it
out.. oops. (I hope the odor did not escape my room.)

Max current is in the 200mA range. (limited by switch...)
Now I'm thinking about ditching the rotary switch and
using a latching relays.. ~$2-3 each (in 100)
Seems like I could do a lot with 3-4.
I'd still have to have inputs.. push buttons I guess..
and led indicators. A front panel pcb...
(rotary switches are on the shelf.)

Sorry for thinking out loud.

George H .

PS,
Phil, Re: 249,499, 1k, 2k, 4.02k
I wish we could "bend the log a bit"
and have 250,500,1k,2k,4k..

GH
Click to expand...

Can you do the current control on the input side, rather than
switching 200 mA? Use an analog mux or a low-current rotary switch.

Does anybody still make R-2R ladder networks? I guess you could make
your own.

Use a DAC?



--

John Larkin Highland Technology, Inc
picosecond timing precision measurement

jlarkin att highlandtechnology dott com
http://www.highlandtechnology.com
 
On 02/29/2016 07:49 PM, George Herold wrote:
On Monday, February 29, 2016 at 2:12:40 PM UTC-5, Phil Hobbs wrote:
On 02/29/2016 11:52 AM, George Herold wrote:
Hi all, I'm making this current output in fixed ratio's... 1,2,4... etc.
I'm using 0.1% RG series from susumu.
There are lots of 1:2 ratio's,
But the only 1:2:4 that I find (in stock at DK)
is 75/150/300. are there any others?

(There is 140/280/560, but 280 is a non-stock item at DK.)

75/150/300 also has 1.2K so a 1:2:4..16 ratio, which look nice.

George H.

Well, 249/499/1000/2000 is close, and
255/510/1020 is nominally exact. (Susumu sells the E24 values in their
precision series as well, iirc.)

Cheers

Phil Hobbs

--
Dr Philip C D Hobbs
Principal Consultant
ElectroOptical Innovations LLC
Optics, Electro-optics, Photonics, Analog Electronics

160 North State Road #203
Briarcliff Manor NY 10510

hobbs at electrooptical dot net
http://electrooptical.net

Tim, Phil, thanks. I had a total brain fart today.
It's an opamp -> fet -> load/resistor_feedback
current source.
I wanted to switch R (with rotary switch) and I thought
I could do it in shunt/ parallel, until I tried to lay it
out.. oops. (I hope the odor did not escape my room.)

Max current is in the 200mA range. (limited by switch...)
Now I'm thinking about ditching the rotary switch and
using a latching relays.. ~$2-3 each (in 100)
Seems like I could do a lot with 3-4.
I'd still have to have inputs.. push buttons I guess..
and led indicators. A front panel pcb...
(rotary switches are on the shelf.)

Sorry for thinking out loud.

George H .

PS,
Phil, Re: 249,499, 1k, 2k, 4.02k
I wish we could "bend the log a bit"
and have 250,500,1k,2k,4k..
Click to expand...

You can bend them a bit by using normal resistors as a small
perturbation, e.g. 249 or 499 ohms 0.1% + 1 ohm 1%, 4.02k 0.1% // 806k 1%.

Cheers

Phil Hobbs
 
On Mon, 29 Feb 2016 17:31:09 -0800, John Larkin wrote:

On Mon, 29 Feb 2016 16:49:53 -0800 (PST), George Herold
gherold@teachspin.com> wrote:

On Monday, February 29, 2016 at 2:12:40 PM UTC-5, Phil Hobbs wrote:
On 02/29/2016 11:52 AM, George Herold wrote:
Hi all, I'm making this current output in fixed ratio's... 1,2,4...
etc.
I'm using 0.1% RG series from susumu.
There are lots of 1:2 ratio's,
But the only 1:2:4 that I find (in stock at DK)
is 75/150/300. are there any others?

(There is 140/280/560, but 280 is a non-stock item at DK.)

75/150/300 also has 1.2K so a 1:2:4..16 ratio, which look nice.

George H.

Well, 249/499/1000/2000 is close, and 255/510/1020 is nominally exact.
(Susumu sells the E24 values in their precision series as well,
iirc.)

Cheers

Phil Hobbs

--
Dr Philip C D Hobbs Principal Consultant ElectroOptical Innovations
LLC Optics, Electro-optics, Photonics, Analog Electronics

160 North State Road #203 Briarcliff Manor NY 10510

hobbs at electrooptical dot net http://electrooptical.net

Tim, Phil, thanks. I had a total brain fart today.
It's an opamp -> fet -> load/resistor_feedback current source.
I wanted to switch R (with rotary switch) and I thought I could do it in
shunt/ parallel, until I tried to lay it out.. oops. (I hope the odor
did not escape my room.)

Max current is in the 200mA range. (limited by switch...)
Now I'm thinking about ditching the rotary switch and using a latching
relays.. ~$2-3 each (in 100)
Seems like I could do a lot with 3-4.
I'd still have to have inputs.. push buttons I guess..
and led indicators. A front panel pcb...
(rotary switches are on the shelf.)

Sorry for thinking out loud.

George H .

PS,
Phil, Re: 249,499, 1k, 2k, 4.02k I wish we could "bend the log a bit"
and have 250,500,1k,2k,4k..

GH




Can you do the current control on the input side, rather than switching
200 mA? Use an analog mux or a low-current rotary switch.

Does anybody still make R-2R ladder networks? I guess you could make
your own.

Use a DAC?
Click to expand...

DigiKey has a bunch of DAC0808s in stock. It looks like it's not the
least bit dead.

--
www.wescottdesign.com
 
On Mon, 29 Feb 2016 21:40:22 -0600, Tim Wescott <tim@seemywebsite.com>
wrote:

On Mon, 29 Feb 2016 17:31:09 -0800, John Larkin wrote:

On Mon, 29 Feb 2016 16:49:53 -0800 (PST), George Herold
gherold@teachspin.com> wrote:

On Monday, February 29, 2016 at 2:12:40 PM UTC-5, Phil Hobbs wrote:
On 02/29/2016 11:52 AM, George Herold wrote:
Hi all, I'm making this current output in fixed ratio's... 1,2,4...
etc.
I'm using 0.1% RG series from susumu.
There are lots of 1:2 ratio's,
But the only 1:2:4 that I find (in stock at DK)
is 75/150/300. are there any others?

(There is 140/280/560, but 280 is a non-stock item at DK.)

75/150/300 also has 1.2K so a 1:2:4..16 ratio, which look nice.

George H.

Well, 249/499/1000/2000 is close, and 255/510/1020 is nominally exact.
(Susumu sells the E24 values in their precision series as well,
iirc.)

Cheers

Phil Hobbs

--
Dr Philip C D Hobbs Principal Consultant ElectroOptical Innovations
LLC Optics, Electro-optics, Photonics, Analog Electronics

160 North State Road #203 Briarcliff Manor NY 10510

hobbs at electrooptical dot net http://electrooptical.net

Tim, Phil, thanks. I had a total brain fart today.
It's an opamp -> fet -> load/resistor_feedback current source.
I wanted to switch R (with rotary switch) and I thought I could do it in
shunt/ parallel, until I tried to lay it out.. oops. (I hope the odor
did not escape my room.)

Max current is in the 200mA range. (limited by switch...)
Now I'm thinking about ditching the rotary switch and using a latching
relays.. ~$2-3 each (in 100)
Seems like I could do a lot with 3-4.
I'd still have to have inputs.. push buttons I guess..
and led indicators. A front panel pcb...
(rotary switches are on the shelf.)

Sorry for thinking out loud.

George H .

PS,
Phil, Re: 249,499, 1k, 2k, 4.02k I wish we could "bend the log a bit"
and have 250,500,1k,2k,4k..

GH




Can you do the current control on the input side, rather than switching
200 mA? Use an analog mux or a low-current rotary switch.

Does anybody still make R-2R ladder networks? I guess you could make
your own.

Use a DAC?

DigiKey has a bunch of DAC0808s in stock. It looks like it's not the
least bit dead.
Click to expand...

There are tons of DACs around, so George could do something to map his
rotary switch into DAC codes. Actually, it's simple 1:1 if he wants
2:1 current steps.

A chopamp would have essentially zero offset error.


--

John Larkin Highland Technology, Inc

lunatic fringe electronics
 
On Monday, February 29, 2016 at 10:40:28 PM UTC-5, Tim Wescott wrote:
On Mon, 29 Feb 2016 17:31:09 -0800, John Larkin wrote:

On Mon, 29 Feb 2016 16:49:53 -0800 (PST), George Herold
gherold@teachspin.com> wrote:

On Monday, February 29, 2016 at 2:12:40 PM UTC-5, Phil Hobbs wrote:
On 02/29/2016 11:52 AM, George Herold wrote:
Hi all, I'm making this current output in fixed ratio's... 1,2,4...
etc.
I'm using 0.1% RG series from susumu.
There are lots of 1:2 ratio's,
But the only 1:2:4 that I find (in stock at DK)
is 75/150/300. are there any others?

(There is 140/280/560, but 280 is a non-stock item at DK.)

75/150/300 also has 1.2K so a 1:2:4..16 ratio, which look nice.

George H.

Well, 249/499/1000/2000 is close, and 255/510/1020 is nominally exact.
(Susumu sells the E24 values in their precision series as well,
iirc.)

Cheers

Phil Hobbs

--
Dr Philip C D Hobbs Principal Consultant ElectroOptical Innovations
LLC Optics, Electro-optics, Photonics, Analog Electronics

160 North State Road #203 Briarcliff Manor NY 10510

hobbs at electrooptical dot net http://electrooptical.net

Tim, Phil, thanks. I had a total brain fart today.
It's an opamp -> fet -> load/resistor_feedback current source.
I wanted to switch R (with rotary switch) and I thought I could do it in
shunt/ parallel, until I tried to lay it out.. oops. (I hope the odor
did not escape my room.)

Max current is in the 200mA range. (limited by switch...)
Now I'm thinking about ditching the rotary switch and using a latching
relays.. ~$2-3 each (in 100)
Seems like I could do a lot with 3-4.
I'd still have to have inputs.. push buttons I guess..
and led indicators. A front panel pcb...
(rotary switches are on the shelf.)

Sorry for thinking out loud.

George H .

PS,
Phil, Re: 249,499, 1k, 2k, 4.02k I wish we could "bend the log a bit"
and have 250,500,1k,2k,4k..

GH




Can you do the current control on the input side, rather than switching
200 mA? Use an analog mux or a low-current rotary switch.

Does anybody still make R-2R ladder networks? I guess you could make
your own.

Use a DAC?

DigiKey has a bunch of DAC0808s in stock. It looks like it's not the
least bit dead.
Click to expand...

I've used an AD7541 in the distant past... "Gack", I didn't
know they were so expensive!

George H.
--
www.wescottdesign.com
Click to expand...
 
On Monday, February 29, 2016 at 11:36:12 PM UTC-5, John Larkin wrote:
On Mon, 29 Feb 2016 21:40:22 -0600, Tim Wescott <tim@seemywebsite.com
wrote:

On Mon, 29 Feb 2016 17:31:09 -0800, John Larkin wrote:

On Mon, 29 Feb 2016 16:49:53 -0800 (PST), George Herold
gherold@teachspin.com> wrote:

On Monday, February 29, 2016 at 2:12:40 PM UTC-5, Phil Hobbs wrote:
On 02/29/2016 11:52 AM, George Herold wrote:
Hi all, I'm making this current output in fixed ratio's... 1,2,4...
etc.
I'm using 0.1% RG series from susumu.
There are lots of 1:2 ratio's,
But the only 1:2:4 that I find (in stock at DK)
is 75/150/300. are there any others?

(There is 140/280/560, but 280 is a non-stock item at DK.)

75/150/300 also has 1.2K so a 1:2:4..16 ratio, which look nice.

George H.

Well, 249/499/1000/2000 is close, and 255/510/1020 is nominally exact.
(Susumu sells the E24 values in their precision series as well,
iirc.)

Cheers

Phil Hobbs

--
Dr Philip C D Hobbs Principal Consultant ElectroOptical Innovations
LLC Optics, Electro-optics, Photonics, Analog Electronics

160 North State Road #203 Briarcliff Manor NY 10510

hobbs at electrooptical dot net http://electrooptical.net

Tim, Phil, thanks. I had a total brain fart today.
It's an opamp -> fet -> load/resistor_feedback current source.
I wanted to switch R (with rotary switch) and I thought I could do it in
shunt/ parallel, until I tried to lay it out.. oops. (I hope the odor
did not escape my room.)

Max current is in the 200mA range. (limited by switch...)
Now I'm thinking about ditching the rotary switch and using a latching
relays.. ~$2-3 each (in 100)
Seems like I could do a lot with 3-4.
I'd still have to have inputs.. push buttons I guess..
and led indicators. A front panel pcb...
(rotary switches are on the shelf.)

Sorry for thinking out loud.

George H .

PS,
Phil, Re: 249,499, 1k, 2k, 4.02k I wish we could "bend the log a bit"
and have 250,500,1k,2k,4k..

GH




Can you do the current control on the input side, rather than switching
200 mA? Use an analog mux or a low-current rotary switch.

Does anybody still make R-2R ladder networks? I guess you could make
your own.

Use a DAC?

DigiKey has a bunch of DAC0808s in stock. It looks like it's not the
least bit dead.

There are tons of DACs around, so George could do something to map his
rotary switch into DAC codes. Actually, it's simple 1:1 if he wants
2:1 current steps.
Click to expand...
I was playing with this idea in bed last night...
The onerous part (for me) would be the user interface.
Push buttons and led indicators.. It's not something I've done,
so I'd have to research, copy and adapt, screw-up, etc...

The switch is too easy... I do still have a bug up my butt with
grayhill switches.. so doing something else is appealing.

George H.
A chopamp would have essentially zero offset error.


--

John Larkin Highland Technology, Inc

lunatic fringe electronics
Click to expand...
 
On Mon, 29 Feb 2016 13:02:59 -0600, Tim Wescott
<seemywebsite@myfooter.really> wrote:

On Mon, 29 Feb 2016 08:52:23 -0800, George Herold wrote:

Hi all, I'm making this current output in fixed ratio's... 1,2,4... etc.
I'm using 0.1% RG series from susumu.
There are lots of 1:2 ratio's,
But the only 1:2:4 that I find (in stock at DK)
is 75/150/300. are there any others?

(There is 140/280/560, but 280 is a non-stock item at DK.)

75/150/300 also has 1.2K so a 1:2:4..16 ratio, which look nice.

George H.

You don't say if you're using the resistors to program a current source
or what, but if you're willing to make an R-2R ladder you can get
1,2,4,8, etc., ad infinitum.

For that matter, you can make a DAC -- but you'd need good resistors.
Click to expand...

My recollection is that R-2R ladder DACs are far less
sensitive to resistor tolerance than 1-2-4-8R-type DACs.
Back in the Olden Days of DOS computer audio, an 8-bit R-2R
ladder made from 10K-20K 5% resistors (driven by a printer
port... remember those?) gave pretty decent sound.

You could even make an 8-bit ADC by wiring the ladder output
to a status input pin on the port. Wire the input signal
through a summing resistor to the same pin, and use SAR
logic to balance the ladder output against the signal at the
gate threshold voltage. The whole thing could be wired into
the parallel port connector hood to get a "passive" ADC
(since the active part was inside the computer).

Ahh, DOS were da days!

Best regards,




Bob Masta

DAQARTA v9.00
Data AcQuisition And Real-Time Analysis
www.daqarta.com
Scope, Spectrum, Spectrogram, Sound Level Meter
Frequency Counter, Pitch Track, Pitch-to-MIDI
FREE 8-channel Signal Generator, DaqMusiq generator
Science with your sound card!
 
On Monday, February 29, 2016 at 11:36:12 PM UTC-5, John Larkin wrote:
On Mon, 29 Feb 2016 21:40:22 -0600, Tim Wescott <tim@seemywebsite.com
wrote:

On Mon, 29 Feb 2016 17:31:09 -0800, John Larkin wrote:

On Mon, 29 Feb 2016 16:49:53 -0800 (PST), George Herold
gherold@teachspin.com> wrote:

On Monday, February 29, 2016 at 2:12:40 PM UTC-5, Phil Hobbs wrote:
On 02/29/2016 11:52 AM, George Herold wrote:
Hi all, I'm making this current output in fixed ratio's... 1,2,4...
etc.
I'm using 0.1% RG series from susumu.
There are lots of 1:2 ratio's,
But the only 1:2:4 that I find (in stock at DK)
is 75/150/300. are there any others?

(There is 140/280/560, but 280 is a non-stock item at DK.)

75/150/300 also has 1.2K so a 1:2:4..16 ratio, which look nice.

George H.

Well, 249/499/1000/2000 is close, and 255/510/1020 is nominally exact.
(Susumu sells the E24 values in their precision series as well,
iirc.)

Cheers

Phil Hobbs

--
Dr Philip C D Hobbs Principal Consultant ElectroOptical Innovations
LLC Optics, Electro-optics, Photonics, Analog Electronics

160 North State Road #203 Briarcliff Manor NY 10510

hobbs at electrooptical dot net http://electrooptical.net

Tim, Phil, thanks. I had a total brain fart today.
It's an opamp -> fet -> load/resistor_feedback current source.
I wanted to switch R (with rotary switch) and I thought I could do it in
shunt/ parallel, until I tried to lay it out.. oops. (I hope the odor
did not escape my room.)

Max current is in the 200mA range. (limited by switch...)
Now I'm thinking about ditching the rotary switch and using a latching
relays.. ~$2-3 each (in 100)
Seems like I could do a lot with 3-4.
I'd still have to have inputs.. push buttons I guess..
and led indicators. A front panel pcb...
(rotary switches are on the shelf.)

Sorry for thinking out loud.

George H .

PS,
Phil, Re: 249,499, 1k, 2k, 4.02k I wish we could "bend the log a bit"
and have 250,500,1k,2k,4k..

GH




Can you do the current control on the input side, rather than switching
200 mA? Use an analog mux or a low-current rotary switch.

Does anybody still make R-2R ladder networks? I guess you could make
your own.

Use a DAC?

DigiKey has a bunch of DAC0808s in stock. It looks like it's not the
least bit dead.

There are tons of DACs around, so George could do something to map his
rotary switch into DAC codes. Actually, it's simple 1:1 if he wants
2:1 current steps.

A chopamp would have essentially zero offset error.
Click to expand...

RE: Chop amp.

Say I was looking through AoE3 for a precision opamp with a bit of speed,
and I cam across the opa192.
http://www.ti.com/lit/ds/symlink/opa192.pdf

Which has got some sweet specs! If someone mentioned this opamp before
then I missed it. Except for this weird extra noise when the input is near
the positive rail, it looks almost "perfect".

George H.

--

John Larkin Highland Technology, Inc

lunatic fringe electronics
Click to expand...
 
On Mon, 29 Feb 2016 20:36:11 -0800, John Larkin wrote:

On Mon, 29 Feb 2016 21:40:22 -0600, Tim Wescott <tim@seemywebsite.com
wrote:

On Mon, 29 Feb 2016 17:31:09 -0800, John Larkin wrote:

On Mon, 29 Feb 2016 16:49:53 -0800 (PST), George Herold
gherold@teachspin.com> wrote:

On Monday, February 29, 2016 at 2:12:40 PM UTC-5, Phil Hobbs wrote:
On 02/29/2016 11:52 AM, George Herold wrote:
Hi all, I'm making this current output in fixed ratio's...
1,2,4...
etc.
I'm using 0.1% RG series from susumu.
There are lots of 1:2 ratio's,
But the only 1:2:4 that I find (in stock at DK)
is 75/150/300. are there any others?

(There is 140/280/560, but 280 is a non-stock item at DK.)

75/150/300 also has 1.2K so a 1:2:4..16 ratio, which look nice.

George H.

Well, 249/499/1000/2000 is close, and 255/510/1020 is nominally
exact.
(Susumu sells the E24 values in their precision series as well,
iirc.)

Cheers

Phil Hobbs

--
Dr Philip C D Hobbs Principal Consultant ElectroOptical Innovations
LLC Optics, Electro-optics, Photonics, Analog Electronics

160 North State Road #203 Briarcliff Manor NY 10510

hobbs at electrooptical dot net http://electrooptical.net

Tim, Phil, thanks. I had a total brain fart today.
It's an opamp -> fet -> load/resistor_feedback current source.
I wanted to switch R (with rotary switch) and I thought I could do it
in shunt/ parallel, until I tried to lay it out.. oops. (I hope the
odor did not escape my room.)

Max current is in the 200mA range. (limited by switch...)
Now I'm thinking about ditching the rotary switch and using a latching
relays.. ~$2-3 each (in 100)
Seems like I could do a lot with 3-4.
I'd still have to have inputs.. push buttons I guess..
and led indicators. A front panel pcb...
(rotary switches are on the shelf.)

Sorry for thinking out loud.

George H .

PS,
Phil, Re: 249,499, 1k, 2k, 4.02k I wish we could "bend the log a bit"
and have 250,500,1k,2k,4k..

GH




Can you do the current control on the input side, rather than
switching 200 mA? Use an analog mux or a low-current rotary switch.

Does anybody still make R-2R ladder networks? I guess you could make
your own.

Use a DAC?

DigiKey has a bunch of DAC0808s in stock. It looks like it's not the
least bit dead.

There are tons of DACs around, so George could do something to map his
rotary switch into DAC codes. Actually, it's simple 1:1 if he wants 2:1
current steps.

A chopamp would have essentially zero offset error.
Click to expand...

You and I are thinking alike here.

--
www.wescottdesign.com
 
On Tue, 01 Mar 2016 06:04:04 -0800, George Herold wrote:

On Monday, February 29, 2016 at 11:36:12 PM UTC-5, John Larkin wrote:
On Mon, 29 Feb 2016 21:40:22 -0600, Tim Wescott <tim@seemywebsite.com
wrote:

On Mon, 29 Feb 2016 17:31:09 -0800, John Larkin wrote:

On Mon, 29 Feb 2016 16:49:53 -0800 (PST), George Herold
gherold@teachspin.com> wrote:

On Monday, February 29, 2016 at 2:12:40 PM UTC-5, Phil Hobbs wrote:
On 02/29/2016 11:52 AM, George Herold wrote:
Hi all, I'm making this current output in fixed ratio's...
1,2,4...
etc.
I'm using 0.1% RG series from susumu.
There are lots of 1:2 ratio's,
But the only 1:2:4 that I find (in stock at DK)
is 75/150/300. are there any others?

(There is 140/280/560, but 280 is a non-stock item at DK.)

75/150/300 also has 1.2K so a 1:2:4..16 ratio, which look nice.

George H.

Well, 249/499/1000/2000 is close, and 255/510/1020 is nominally
exact.
(Susumu sells the E24 values in their precision series as well,
iirc.)

Cheers

Phil Hobbs

--
Dr Philip C D Hobbs Principal Consultant ElectroOptical
Innovations LLC Optics, Electro-optics, Photonics, Analog
Electronics

160 North State Road #203 Briarcliff Manor NY 10510

hobbs at electrooptical dot net http://electrooptical.net

Tim, Phil, thanks. I had a total brain fart today.
It's an opamp -> fet -> load/resistor_feedback current source.
I wanted to switch R (with rotary switch) and I thought I could do
it in shunt/ parallel, until I tried to lay it out.. oops. (I hope
the odor did not escape my room.)

Max current is in the 200mA range. (limited by switch...)
Now I'm thinking about ditching the rotary switch and using a
latching relays.. ~$2-3 each (in 100)
Seems like I could do a lot with 3-4.
I'd still have to have inputs.. push buttons I guess..
and led indicators. A front panel pcb...
(rotary switches are on the shelf.)

Sorry for thinking out loud.

George H .

PS,
Phil, Re: 249,499, 1k, 2k, 4.02k I wish we could "bend the log a
bit" and have 250,500,1k,2k,4k..

GH




Can you do the current control on the input side, rather than
switching 200 mA? Use an analog mux or a low-current rotary switch.

Does anybody still make R-2R ladder networks? I guess you could make
your own.

Use a DAC?

DigiKey has a bunch of DAC0808s in stock. It looks like it's not the
least bit dead.

There are tons of DACs around, so George could do something to map his
rotary switch into DAC codes. Actually, it's simple 1:1 if he wants 2:1
current steps.

I was playing with this idea in bed last night...
The onerous part (for me) would be the user interface.
Push buttons and led indicators.. It's not something I've done,
so I'd have to research, copy and adapt, screw-up, etc...

The switch is too easy... I do still have a bug up my butt with grayhill
switches.. so doing something else is appealing.
Click to expand...

Yes, but if you want 2:1 ratios, then all you need to do is turn on one
pin of the DAC at a time, in order.


--
www.wescottdesign.com
 
On Tue, 01 Mar 2016 10:41:18 -0600, Tim Wescott <tim@seemywebsite.com>
wrote:

On Mon, 29 Feb 2016 20:36:11 -0800, John Larkin wrote:

On Mon, 29 Feb 2016 21:40:22 -0600, Tim Wescott <tim@seemywebsite.com
wrote:

On Mon, 29 Feb 2016 17:31:09 -0800, John Larkin wrote:

On Mon, 29 Feb 2016 16:49:53 -0800 (PST), George Herold
gherold@teachspin.com> wrote:

On Monday, February 29, 2016 at 2:12:40 PM UTC-5, Phil Hobbs wrote:
On 02/29/2016 11:52 AM, George Herold wrote:
Hi all, I'm making this current output in fixed ratio's...
1,2,4...
etc.
I'm using 0.1% RG series from susumu.
There are lots of 1:2 ratio's,
But the only 1:2:4 that I find (in stock at DK)
is 75/150/300. are there any others?

(There is 140/280/560, but 280 is a non-stock item at DK.)

75/150/300 also has 1.2K so a 1:2:4..16 ratio, which look nice.

George H.

Well, 249/499/1000/2000 is close, and 255/510/1020 is nominally
exact.
(Susumu sells the E24 values in their precision series as well,
iirc.)

Cheers

Phil Hobbs

--
Dr Philip C D Hobbs Principal Consultant ElectroOptical Innovations
LLC Optics, Electro-optics, Photonics, Analog Electronics

160 North State Road #203 Briarcliff Manor NY 10510

hobbs at electrooptical dot net http://electrooptical.net

Tim, Phil, thanks. I had a total brain fart today.
It's an opamp -> fet -> load/resistor_feedback current source.
I wanted to switch R (with rotary switch) and I thought I could do it
in shunt/ parallel, until I tried to lay it out.. oops. (I hope the
odor did not escape my room.)

Max current is in the 200mA range. (limited by switch...)
Now I'm thinking about ditching the rotary switch and using a latching
relays.. ~$2-3 each (in 100)
Seems like I could do a lot with 3-4.
I'd still have to have inputs.. push buttons I guess..
and led indicators. A front panel pcb...
(rotary switches are on the shelf.)

Sorry for thinking out loud.

George H .

PS,
Phil, Re: 249,499, 1k, 2k, 4.02k I wish we could "bend the log a bit"
and have 250,500,1k,2k,4k..

GH




Can you do the current control on the input side, rather than
switching 200 mA? Use an analog mux or a low-current rotary switch.

Does anybody still make R-2R ladder networks? I guess you could make
your own.

Use a DAC?

DigiKey has a bunch of DAC0808s in stock. It looks like it's not the
least bit dead.

There are tons of DACs around, so George could do something to map his
rotary switch into DAC codes. Actually, it's simple 1:1 if he wants 2:1
current steps.

A chopamp would have essentially zero offset error.

You and I are thinking alike here.
Click to expand...

There is something steampunk and nostalgic about rotary switches. But
the switch and knob can get expensive these days, not to mention
wiring.


--

John Larkin Highland Technology, Inc

lunatic fringe electronics
 
On Tue, 1 Mar 2016 05:48:35 -0800 (PST), George Herold
<gherold@teachspin.com> wrote:

On Monday, February 29, 2016 at 10:40:28 PM UTC-5, Tim Wescott wrote:
On Mon, 29 Feb 2016 17:31:09 -0800, John Larkin wrote:

On Mon, 29 Feb 2016 16:49:53 -0800 (PST), George Herold
gherold@teachspin.com> wrote:

On Monday, February 29, 2016 at 2:12:40 PM UTC-5, Phil Hobbs wrote:
On 02/29/2016 11:52 AM, George Herold wrote:
Hi all, I'm making this current output in fixed ratio's... 1,2,4...
etc.
I'm using 0.1% RG series from susumu.
There are lots of 1:2 ratio's,
But the only 1:2:4 that I find (in stock at DK)
is 75/150/300. are there any others?

(There is 140/280/560, but 280 is a non-stock item at DK.)

75/150/300 also has 1.2K so a 1:2:4..16 ratio, which look nice.

George H.

Well, 249/499/1000/2000 is close, and 255/510/1020 is nominally exact.
(Susumu sells the E24 values in their precision series as well,
iirc.)

Cheers

Phil Hobbs

--
Dr Philip C D Hobbs Principal Consultant ElectroOptical Innovations
LLC Optics, Electro-optics, Photonics, Analog Electronics

160 North State Road #203 Briarcliff Manor NY 10510

hobbs at electrooptical dot net http://electrooptical.net

Tim, Phil, thanks. I had a total brain fart today.
It's an opamp -> fet -> load/resistor_feedback current source.
I wanted to switch R (with rotary switch) and I thought I could do it in
shunt/ parallel, until I tried to lay it out.. oops. (I hope the odor
did not escape my room.)

Max current is in the 200mA range. (limited by switch...)
Now I'm thinking about ditching the rotary switch and using a latching
relays.. ~$2-3 each (in 100)
Seems like I could do a lot with 3-4.
I'd still have to have inputs.. push buttons I guess..
and led indicators. A front panel pcb...
(rotary switches are on the shelf.)

Sorry for thinking out loud.

George H .

PS,
Phil, Re: 249,499, 1k, 2k, 4.02k I wish we could "bend the log a bit"
and have 250,500,1k,2k,4k..

GH




Can you do the current control on the input side, rather than switching
200 mA? Use an analog mux or a low-current rotary switch.

Does anybody still make R-2R ladder networks? I guess you could make
your own.

Use a DAC?

DigiKey has a bunch of DAC0808s in stock. It looks like it's not the
least bit dead.

I've used an AD7541 in the distant past... "Gack", I didn't
know they were so expensive!

George H.
Click to expand...

Yikes, that is pricey. Serial DACs are cheap, but I guess you want
parallel. We're paying $4.40 for AD5440, a dual 10-bit parallel DAC.
There are probably cheaper singles, maybe 8 bits. That DAC0808 is 69
cents in quantity and might be accurate enough.

Chopamps: ADA4638 handles +-15 supplies and costs about $2. Lower
voltage chopamps like AD8628 are cheaper.


--

John Larkin Highland Technology, Inc

lunatic fringe electronics
 
On Wed, 02 Mar 2016 05:54:56 -0800, John Larkin wrote:

On Tue, 01 Mar 2016 10:41:18 -0600, Tim Wescott <tim@seemywebsite.com
wrote:

On Mon, 29 Feb 2016 20:36:11 -0800, John Larkin wrote:

On Mon, 29 Feb 2016 21:40:22 -0600, Tim Wescott <tim@seemywebsite.com
wrote:

On Mon, 29 Feb 2016 17:31:09 -0800, John Larkin wrote:

On Mon, 29 Feb 2016 16:49:53 -0800 (PST), George Herold
gherold@teachspin.com> wrote:

On Monday, February 29, 2016 at 2:12:40 PM UTC-5, Phil Hobbs wrote:
On 02/29/2016 11:52 AM, George Herold wrote:
Hi all, I'm making this current output in fixed ratio's...
1,2,4...
etc.
I'm using 0.1% RG series from susumu.
There are lots of 1:2 ratio's,
But the only 1:2:4 that I find (in stock at DK)
is 75/150/300. are there any others?

(There is 140/280/560, but 280 is a non-stock item at DK.)

75/150/300 also has 1.2K so a 1:2:4..16 ratio, which look nice.

George H.

Well, 249/499/1000/2000 is close, and 255/510/1020 is nominally
exact.
(Susumu sells the E24 values in their precision series as well,
iirc.)

Cheers

Phil Hobbs

--
Dr Philip C D Hobbs Principal Consultant ElectroOptical
Innovations LLC Optics, Electro-optics, Photonics, Analog
Electronics

160 North State Road #203 Briarcliff Manor NY 10510

hobbs at electrooptical dot net http://electrooptical.net

Tim, Phil, thanks. I had a total brain fart today.
It's an opamp -> fet -> load/resistor_feedback current source.
I wanted to switch R (with rotary switch) and I thought I could do
it in shunt/ parallel, until I tried to lay it out.. oops. (I hope
the odor did not escape my room.)

Max current is in the 200mA range. (limited by switch...)
Now I'm thinking about ditching the rotary switch and using a
latching relays.. ~$2-3 each (in 100)
Seems like I could do a lot with 3-4.
I'd still have to have inputs.. push buttons I guess..
and led indicators. A front panel pcb...
(rotary switches are on the shelf.)

Sorry for thinking out loud.

George H .

PS,
Phil, Re: 249,499, 1k, 2k, 4.02k I wish we could "bend the log a
bit" and have 250,500,1k,2k,4k..

GH




Can you do the current control on the input side, rather than
switching 200 mA? Use an analog mux or a low-current rotary switch.

Does anybody still make R-2R ladder networks? I guess you could make
your own.

Use a DAC?

DigiKey has a bunch of DAC0808s in stock. It looks like it's not the
least bit dead.

There are tons of DACs around, so George could do something to map his
rotary switch into DAC codes. Actually, it's simple 1:1 if he wants
2:1 current steps.

A chopamp would have essentially zero offset error.

You and I are thinking alike here.

There is something steampunk and nostalgic about rotary switches. But
the switch and knob can get expensive these days, not to mention wiring.
Click to expand...

I know. It's lowering, but every time I end up doing a full-system
design the case, knobs and buttons end up costing more than the circuitry.

--

Tim Wescott
Wescott Design Services
http://www.wescottdesign.com
 
On Wed, 02 Mar 2016 12:23:52 -0600, Tim Wescott
<seemywebsite@myfooter.really> wrote:

On Wed, 02 Mar 2016 05:54:56 -0800, John Larkin wrote:

On Tue, 01 Mar 2016 10:41:18 -0600, Tim Wescott <tim@seemywebsite.com
wrote:

On Mon, 29 Feb 2016 20:36:11 -0800, John Larkin wrote:

On Mon, 29 Feb 2016 21:40:22 -0600, Tim Wescott <tim@seemywebsite.com
wrote:

On Mon, 29 Feb 2016 17:31:09 -0800, John Larkin wrote:

On Mon, 29 Feb 2016 16:49:53 -0800 (PST), George Herold
gherold@teachspin.com> wrote:

On Monday, February 29, 2016 at 2:12:40 PM UTC-5, Phil Hobbs wrote:
On 02/29/2016 11:52 AM, George Herold wrote:
Hi all, I'm making this current output in fixed ratio's...
1,2,4...
etc.
I'm using 0.1% RG series from susumu.
There are lots of 1:2 ratio's,
But the only 1:2:4 that I find (in stock at DK)
is 75/150/300. are there any others?

(There is 140/280/560, but 280 is a non-stock item at DK.)

75/150/300 also has 1.2K so a 1:2:4..16 ratio, which look nice.

George H.

Well, 249/499/1000/2000 is close, and 255/510/1020 is nominally
exact.
(Susumu sells the E24 values in their precision series as well,
iirc.)

Cheers

Phil Hobbs

--
Dr Philip C D Hobbs Principal Consultant ElectroOptical
Innovations LLC Optics, Electro-optics, Photonics, Analog
Electronics

160 North State Road #203 Briarcliff Manor NY 10510

hobbs at electrooptical dot net http://electrooptical.net

Tim, Phil, thanks. I had a total brain fart today.
It's an opamp -> fet -> load/resistor_feedback current source.
I wanted to switch R (with rotary switch) and I thought I could do
it in shunt/ parallel, until I tried to lay it out.. oops. (I hope
the odor did not escape my room.)

Max current is in the 200mA range. (limited by switch...)
Now I'm thinking about ditching the rotary switch and using a
latching relays.. ~$2-3 each (in 100)
Seems like I could do a lot with 3-4.
I'd still have to have inputs.. push buttons I guess..
and led indicators. A front panel pcb...
(rotary switches are on the shelf.)

Sorry for thinking out loud.

George H .

PS,
Phil, Re: 249,499, 1k, 2k, 4.02k I wish we could "bend the log a
bit" and have 250,500,1k,2k,4k..

GH




Can you do the current control on the input side, rather than
switching 200 mA? Use an analog mux or a low-current rotary switch.

Does anybody still make R-2R ladder networks? I guess you could make
your own.

Use a DAC?

DigiKey has a bunch of DAC0808s in stock. It looks like it's not the
least bit dead.

There are tons of DACs around, so George could do something to map his
rotary switch into DAC codes. Actually, it's simple 1:1 if he wants
2:1 current steps.

A chopamp would have essentially zero offset error.

You and I are thinking alike here.

There is something steampunk and nostalgic about rotary switches. But
the switch and knob can get expensive these days, not to mention wiring.

I know. It's lowering, but every time I end up doing a full-system
design the case, knobs and buttons end up costing more than the circuitry.
Click to expand...

Well, buy more expensive parts!

We've found that designing our own box, and having a shop
punch/bend/anodize the sheet metal, is cheaper than buying a
commercial box, much less machining it.


--

John Larkin Highland Technology, Inc
picosecond timing precision measurement

jlarkin att highlandtechnology dott com
http://www.highlandtechnology.com
 
You must log in or register to reply here.

Welcome to EDABoard.com

Sponsor

Back
Top