Looking for a way to remotely measre 12v and 24v with a sing

[Steve]

I have been a lurker in this group for some time. This is a totally
non-political post.

I have a remote controlled gate located around 150' from the house. The gate
runs off 24VDC, and the electronics runs off 12VDC. The 12V is being supplied
by a 24V to 12V switching power supply. Right now, I am getting a solid 12V
(measured) from the power supply.

The 24V power is being fed to the gate by 2 #8 wires from a 24V battery-backup
power supply in the house. The voltage drop on these wires is negligible, and I
am getting a solid 24V (measured) at the gate..

I would like to remotely measure both the 24V and 12V at the gate.

Right now, I have a single free wire going between the gate and the house that I
can use without pulling more cable. The wire is now connected to the 24V supply
at the gate, and a voltmeter in the house, but I would like to monitor both the
24V supply and the 12V supply, and don't want to pull more cable between the
house and gate.

Does anyone know of a simple and cheap way to monitor both voltages using only
the one wire? Ground is available through a number of cables, so, ground
reference is not an issue.

Thanks in advance.

Steve

 

[John Larkin]

On Wed, 08 Apr 2020 16:00:32 -0400, Steve <nospam@nowhere.org> wrote:

I have been a lurker in this group for some time. This is a totally
non-political post.

I have a remote controlled gate located around 150' from the house. The gate
runs off 24VDC, and the electronics runs off 12VDC. The 12V is being supplied
by a 24V to 12V switching power supply. Right now, I am getting a solid 12V
(measured) from the power supply.

The 24V power is being fed to the gate by 2 #8 wires from a 24V battery-backup
power supply in the house. The voltage drop on these wires is negligible, and I
am getting a solid 24V (measured) at the gate..

I would like to remotely measure both the 24V and 12V at the gate.

Right now, I have a single free wire going between the gate and the house that I
can use without pulling more cable. The wire is now connected to the 24V supply
at the gate, and a voltmeter in the house, but I would like to monitor both the
24V supply and the 12V supply, and don't want to pull more cable between the
house and gate.

Does anyone know of a simple and cheap way to monitor both voltages using only
the one wire? Ground is available through a number of cables, so, ground
reference is not an issue.

Thanks in advance.

Steve

A resistor and a diode could provide you a source that is 24 volts if
unloaded, and drops to 12 when loaded. On the DVM end, the load could
be a resistor and a pushbutton.

Something fancier could alternate the voltages.

But if the 12 volts looks OK, isn't it very probable that the 24 is OK
too?


--

John Larkin Highland Technology, Inc
picosecond timing precision measurement

jlarkin att highlandtechnology dott com
http://www.highlandtechnology.com

 

[Sjouke Burry]

On 08.04.20 22:00, Steve wrote:

I have been a lurker in this group for some time. This is a totally
non-political post.

I have a remote controlled gate located around 150' from the house. The gate
runs off 24VDC, and the electronics runs off 12VDC. The 12V is being supplied
by a 24V to 12V switching power supply. Right now, I am getting a solid 12V
(measured) from the power supply.

The 24V power is being fed to the gate by 2 #8 wires from a 24V battery-backup
power supply in the house. The voltage drop on these wires is negligible, and I
am getting a solid 24V (measured) at the gate..

I would like to remotely measure both the 24V and 12V at the gate.

Right now, I have a single free wire going between the gate and the house that I
can use without pulling more cable. The wire is now connected to the 24V supply
at the gate, and a voltmeter in the house, but I would like to monitor both the
24V supply and the 12V supply, and don't want to pull more cable between the
house and gate.

Does anyone know of a simple and cheap way to monitor both voltages using only
the one wire? Ground is available through a number of cables, so, ground
reference is not an issue.

Thanks in advance.

Steve

A timer and a relay to switch between the voltages.

 

[Winfield Hill]

Steve wrote...

I have been a lurker in this group for some time.
This is a totally non-political post.

Oh, then you should have marked it OT:

I have a remote controlled gate located around 150'
from the house. The gate runs off 24VDC, and the
electronics runs off 12VDC. ...

John's resistor + diode suggestion is good.


--
Thanks,
- Win

 

[Dave Platt]

In article <jcas8ft928sduuo6mspo6v1f71idoe8846@4ax.com>,
Steve <nospam@nowhere.org> wrote:

Does anyone know of a simple and cheap way to monitor both voltages using only
the one wire? Ground is available through a number of cables, so, ground
reference is not an issue.

Fundamentally you'e going to need some sort of multiplexing approach.
You could do it with a chopper circuit (switching that one line back
and forth between the two voltages) and measure the resulting waveform
indoors.

It might be simpler to move the measurement out to the gate. There
are any number of little flea-bite microcontrollers that have onboard
analog-to-digital controllers, and have multiple pins that can select
the voltage to be digitized. You could:

- Power one of these from the voltages in question, maybe through a
pair of diodes and a 78L05 regulator (the micro would run as long
as either voltage is "live").

- Use four resistors to form two voltage dividers, to step down the 12
and 24 volts to a range that's within the micro's limits.

- Write a bit of code to digitize the voltages (alternating between
them) and send the resulting values back to the house by using the
micro's UART pin to transmit ASCII or binary.

 

[whit3rd]

On Wednesday, April 8, 2020 at 1:25:09 PM UTC-7, John Larkin wrote:

On Wed, 08 Apr 2020 16:00:32 -0400, Steve <nospam@nowhere.org> wrote:

I have been a lurker in this group for some time. This is a totally
non-political post.

I have a remote controlled gate located around 150' from the house. The gate
runs off 24VDC, and the electronics runs off 12VDC. The 12V is being supplied
by a 24V to 12V switching power supply. Right now, I am getting a solid 12V
(measured) from the power supply.

The 24V power is being fed to the gate by 2 #8 wires from a 24V battery-backup
power supply in the house. The voltage drop on these wires is negligible, and I
am getting a solid 24V (measured) at the gate..

I would like to remotely measure both the 24V and 12V at the gate.

An oscillator (could be a 74HC14 based, but a '555 would work too) can
be powered from one supply to generate a 1 kHz tone, and from the other to
generate a 10 kHz tone. Let each oscillator free-run, and
you can use a filter and an earbud to pick up the tone of choice. from the
main power cables if you like (a series transformer that saturates, but doesn't burn
up, when major current is drawn would facilitate that).

The old LM567 tone decoder, too, could pick up its programmed frequency
from the midst of noise, and flash a 'power good' light, if you want to
use that 'spare' wire. You could add 'gate open', 'locked' and other
indicators, just arrange a little separation between the different frequencies.

<https://www.ti.com/lit/ds/symlink/lm567c.pdf>

 

[Ricky C]

On Wednesday, April 8, 2020 at 9:24:49 PM UTC-4, whit3rd wrote:

On Wednesday, April 8, 2020 at 1:25:09 PM UTC-7, John Larkin wrote:
On Wed, 08 Apr 2020 16:00:32 -0400, Steve <nospam@nowhere.org> wrote:

I have been a lurker in this group for some time. This is a totally
non-political post.

I have a remote controlled gate located around 150' from the house. The gate
runs off 24VDC, and the electronics runs off 12VDC. The 12V is being supplied
by a 24V to 12V switching power supply. Right now, I am getting a solid 12V
(measured) from the power supply.

The 24V power is being fed to the gate by 2 #8 wires from a 24V battery-backup
power supply in the house. The voltage drop on these wires is negligible, and I
am getting a solid 24V (measured) at the gate..

I would like to remotely measure both the 24V and 12V at the gate.

An oscillator (could be a 74HC14 based, but a '555 would work too) can
be powered from one supply to generate a 1 kHz tone, and from the other to
generate a 10 kHz tone. Let each oscillator free-run, and
you can use a filter and an earbud to pick up the tone of choice. from the
main power cables if you like (a series transformer that saturates, but doesn't burn
up, when major current is drawn would facilitate that).

The old LM567 tone decoder, too, could pick up its programmed frequency
from the midst of noise, and flash a 'power good' light, if you want to
use that 'spare' wire. You could add 'gate open', 'locked' and other
indicators, just arrange a little separation between the different frequencies.

https://www.ti.com/lit/ds/symlink/lm567c.pdf

If you are going to get that complicated, just toss a tiny MCU at it. Have it measure the two voltages and send ASCII data over the wire.

The resistor and diode is probably the best analog solution. It requires nothing to measure the voltages but a volt meter and a resistor. Too bad the resistor is needed. The MCU approach requires even more circuitry at the receiving end, at least a USB to serial port cable and a phone/computer, but way more cooler than a meter.

Or if you want to get a bit fancier, spend another $10 and use an MCU module that has Bluetooth or WiFi built in and connect wirelessly! Wifi won't work at 150 feet, but Bluetooth will. My car remote is Bluetooth and it has an amazing range (it's needed for summon mode). Pull the extra conductor out of the cable and scrap it to help defray the cost of the MCU board.

You can tie it to your house computer and make it available over the Internet. Let others see what your day to day gate voltages are. Goolgeads will help you pay your electric bill to keep it all running.

--

Rick C.

- Get 1,000 miles of free Supercharging
- Tesla referral code - https://ts.la/richard11209

 

[mpm]

On Wednesday, April 8, 2020 at 4:25:09 PM UTC-4, John Larkin wrote:

> >I would like to remotely measure both the 24V and 12V at the gate.

How about using an R2R ladder circuit and two opto-couplers.
Bias them so that the opto's are ON when the voltage is present.

Then, read directly off the R2R.

This arrangement would reliably read all (4) possible states of the two voltages at the gate, and return the result over one wire back to the house.

 

[whit3rd]

On Wednesday, April 8, 2020 at 7:41:52 PM UTC-7, mpm wrote:

On Wednesday, April 8, 2020 at 4:25:09 PM UTC-4, John Larkin wrote:

I would like to remotely measure both the 24V and 12V at the gate.

How about using an R2R ladder circuit and two opto-couplers.
Bias them so that the opto's are ON when the voltage is present.

Then, read directly off the R2R.

yeah, and you can set up a bar-graph LED display with both-good lighting
GREEN, one-good lighting YELLOW, and neither-good lighting RED.
Those indicators are the key to getting user comprehension of the info
on display (the resistor/diode takes some notebooks and a voltmeter; not
for everybody).

When half an experiment is locked behind radiation shielding, the general solution is
a videocam. Anyone can check positions, settings, and readouts who knows
which channel on the site feed covers their 'hot' side, and it doesn't take
training for the drop-in users. It also doesn't have to be pre-planned specific
to the latest changes. Heck, leave a business card in the field of view with your
cell number just in case...

 

[Adrian Tuddenham]

Steve <nospam@nowhere.org> wrote:

I have been a lurker in this group for some time. This is a totally
non-political post.

I have a remote controlled gate located around 150' from the house. The
gate runs off 24VDC, and the electronics runs off 12VDC. The 12V is being
supplied by a 24V to 12V switching power supply. Right now, I am getting
a solid 12V (measured) from the power supply.

The 24V power is being fed to the gate by 2 #8 wires from a 24V
battery-backup power supply in the house. The voltage drop on these wires
is negligible, and I am getting a solid 24V (measured) at the gate..

I would like to remotely measure both the 24V and 12V at the gate.

Right now, I have a single free wire going between the gate and the house
that I can use without pulling more cable. The wire is now connected to
the 24V supply at the gate, and a voltmeter in the house, but I would like
to monitor both the 24V supply and the 12V supply, and don't want to pull
more cable between the house and gate.

Does anyone know of a simple and cheap way to monitor both voltages using
only the one wire? Ground is available through a number of cables, so,
ground reference is not an issue.

It's a bit long-winded, but if you could take a few turns of the supply
wires through a transformer at each end and superimpose A.C. on them,
you could return a signal up the power wiring without needing any
additional wires. A pair of two-transistor multivibrators, one on each
power rail, could generate different audio frequency signals -- the
amplitudes of the signals could then be detected by selective amplifiers
at the house end.

The cheapness or otherwise would depend on what you had lying around in
your spares box.

--
~ Adrian Tuddenham ~
(Remove the ".invalid"s and add ".co.uk" to reply)
www.poppyrecords.co.uk

 

[Jasen Betts]

On 2020-04-08, Sjouke Burry <burrynulnulfour@ppllaanneett.nnll> wrote:

On 08.04.20 22:00, Steve wrote:
I have been a lurker in this group for some time. This is a totally
non-political post.

I have a remote controlled gate located around 150' from the house. The gate
runs off 24VDC, and the electronics runs off 12VDC. The 12V is being supplied
by a 24V to 12V switching power supply. Right now, I am getting a solid 12V
(measured) from the power supply.

The 24V power is being fed to the gate by 2 #8 wires from a 24V battery-backup
power supply in the house. The voltage drop on these wires is negligible, and I
am getting a solid 24V (measured) at the gate..

I would like to remotely measure both the 24V and 12V at the gate.

Right now, I have a single free wire going between the gate and the house that I
can use without pulling more cable. The wire is now connected to the 24V supply
at the gate, and a voltmeter in the house, but I would like to monitor both the
24V supply and the 12V supply, and don't want to pull more cable between the
house and gate.

Does anyone know of a simple and cheap way to monitor both voltages using only
the one wire? Ground is available through a number of cables, so, ground
reference is not an issue.

Thanks in advance.

Steve

A timer and a relay to switch between the voltages.

Or a relaxation oscillator between the +24 and +12
7555 or something like that.

--
Jasen.

 

On Wednesday, April 8, 2020 at 4:25:09 PM UTC-4, John Larkin wrote:

On Wed, 08 Apr 2020 16:00:32 -0400, Steve <nospam@nowhere.org> wrote:

I have been a lurker in this group for some time. This is a totally
non-political post.

I have a remote controlled gate located around 150' from the house. The gate
runs off 24VDC, and the electronics runs off 12VDC. The 12V is being supplied
by a 24V to 12V switching power supply. Right now, I am getting a solid 12V
(measured) from the power supply.

The 24V power is being fed to the gate by 2 #8 wires from a 24V battery-backup
power supply in the house. The voltage drop on these wires is negligible, and I
am getting a solid 24V (measured) at the gate..

I would like to remotely measure both the 24V and 12V at the gate.

Right now, I have a single free wire going between the gate and the house that I
can use without pulling more cable. The wire is now connected to the 24V supply
at the gate, and a voltmeter in the house, but I would like to monitor both the
24V supply and the 12V supply, and don't want to pull more cable between the
house and gate.

Does anyone know of a simple and cheap way to monitor both voltages using only
the one wire? Ground is available through a number of cables, so, ground
reference is not an issue.

Thanks in advance.

Steve

A resistor and a diode could provide you a source that is 24 volts if
unloaded, and drops to 12 when loaded. On the DVM end, the load could
be a resistor and a pushbutton.

Something fancier could alternate the voltages.

But if the 12 volts looks OK, isn't it very probable that the 24 is OK
too?


--

John Larkin Highland Technology, Inc
picosecond timing precision measurement

jlarkin att highlandtechnology dott com
http://www.highlandtechnology.com

Use a resistor divider between 24V and 12V. You should get 18V. Send the 18V back to the hose and set up to comparators in your house to monitor over18V and under 18V

 

[Phil Hobbs]

On 2020-04-08 16:00, Steve wrote:

I have been a lurker in this group for some time. This is a totally
non-political post.

I have a remote controlled gate located around 150' from the house. The gate
runs off 24VDC, and the electronics runs off 12VDC. The 12V is being supplied
by a 24V to 12V switching power supply. Right now, I am getting a solid 12V
(measured) from the power supply.

The 24V power is being fed to the gate by 2 #8 wires from a 24V battery-backup
power supply in the house. The voltage drop on these wires is negligible, and I
am getting a solid 24V (measured) at the gate..

I would like to remotely measure both the 24V and 12V at the gate.

Right now, I have a single free wire going between the gate and the house that I
can use without pulling more cable. The wire is now connected to the 24V supply
at the gate, and a voltmeter in the house, but I would like to monitor both the
24V supply and the 12V supply, and don't want to pull more cable between the
house and gate.

Does anyone know of a simple and cheap way to monitor both voltages using only
the one wire? Ground is available through a number of cables, so, ground
reference is not an issue.

Thanks in advance.

Steve

One approach would be to use a latching 12-V DPST (Form C) relay.
Connect the pole and a 1-uF ceramic cap to the long wire, and connect
the throws to +12 and +24. Wire the coil as shown.

sense 10k 0----+12V
wire
0----*---RRRR---O
| \
CCC / 0----+24V
CCC 10uF /
| /
C /
O /
I
L
|
GND

And on the other end, a couple of pushbuttons and a DVM:

+24V S1
|
*-> |
|--
*-> |
|
|
0---------*------------------*
| S2 |
*-> | DVM
|-- DVM
*-> | |
| GND
+12V


Push one button for +12, and the other one for +24. Don't push both at
once. (To get fancier, you can use a MOM-OFF-MOM toggle switch
instead of the pushbuttons.)

That way, you put a nice beefy pulse on the sense wire that switches the
relay, then after a second or so you can get a good measurement.

Make sure the coil is the right way round--you want a positive pulse to
make it connect to the +24V side. That way, when it's reading +12 and
you push S1, you put +12V across the coil, and it'll switch to reading
+24. When you push S2, there's +24V on the cap, so the coil sees a
pulse of -12V and so switches to measuring +12V. You could also just
ground S2. That'll overvolt the coil a little going from 24V to 12V,
but that shouldn't hurt anything much.

You may need to experiment with the size of the capacitor. A 9-volt
relay would get you a bit more margin, which helps when pulling this
sort of stunt. Obviously this will stop working at some point when the
supply fails or the batteries get too flat.

I once did something like this with two relays so that I could bootstrap
the coil-to-contact capacitance in an ultra-high-Z front end.

Cheers

Phil Hobbs

--
Dr Philip C D Hobbs
Principal Consultant
ElectroOptical Innovations LLC / Hobbs ElectroOptics
Optics, Electro-optics, Photonics, Analog Electronics
Briarcliff Manor NY 10510

http://electrooptical.net
http://hobbs-eo.com

 

[Joe Chisolm]

On Wed, 08 Apr 2020 16:00:32 -0400, Steve wrote:

I have been a lurker in this group for some time. This is a totally
non-political post.

I have a remote controlled gate located around 150' from the house. The
gate runs off 24VDC, and the electronics runs off 12VDC. The 12V is
being supplied by a 24V to 12V switching power supply. Right now, I am
getting a solid 12V (measured) from the power supply.

The 24V power is being fed to the gate by 2 #8 wires from a 24V
battery-backup power supply in the house. The voltage drop on these
wires is negligible, and I am getting a solid 24V (measured) at the
gate..

I would like to remotely measure both the 24V and 12V at the gate.

Right now, I have a single free wire going between the gate and the
house that I can use without pulling more cable. The wire is now
connected to the 24V supply at the gate, and a voltmeter in the house,
but I would like to monitor both the 24V supply and the 12V supply, and
don't want to pull more cable between the house and gate.

Does anyone know of a simple and cheap way to monitor both voltages
using only the one wire? Ground is available through a number of
cables, so, ground reference is not an issue.

Thanks in advance.

Steve

Since the 12 is derived from the 24 you have 3 states
no 24 and therefore no 12
24 but no 12
24 and 12

Take the 24 and run through a 4:1 divider and a diode and
say a 10K load in at the house. If 24 is good you read
about 6V - diode drop.
Take the 12 through a diode and tie the 2 diode K together.

no 24: you read zero across your 10K load
24 but no 12: you read about 6 across your load
24 & 12: you read about 12 across your load


--
Chisolm
Texas-American

 

[George Herold]

On Wednesday, April 8, 2020 at 4:25:09 PM UTC-4, John Larkin wrote:

On Wed, 08 Apr 2020 16:00:32 -0400, Steve <nospam@nowhere.org> wrote:

I have been a lurker in this group for some time. This is a totally
non-political post.

I have a remote controlled gate located around 150' from the house. The gate
runs off 24VDC, and the electronics runs off 12VDC. The 12V is being supplied
by a 24V to 12V switching power supply. Right now, I am getting a solid 12V
(measured) from the power supply.

The 24V power is being fed to the gate by 2 #8 wires from a 24V battery-backup
power supply in the house. The voltage drop on these wires is negligible, and I
am getting a solid 24V (measured) at the gate..

I would like to remotely measure both the 24V and 12V at the gate.

Right now, I have a single free wire going between the gate and the house that I
can use without pulling more cable. The wire is now connected to the 24V supply
at the gate, and a voltmeter in the house, but I would like to monitor both the
24V supply and the 12V supply, and don't want to pull more cable between the
house and gate.

Does anyone know of a simple and cheap way to monitor both voltages using only
the one wire? Ground is available through a number of cables, so, ground
reference is not an issue.

Thanks in advance.

Steve

A resistor and a diode could provide you a source that is 24 volts if
unloaded, and drops to 12 when loaded. On the DVM end, the load could
be a resistor and a pushbutton.

Nice. I was thinking of two current setting R's on the supplies,
and then a current measuring resistor back where you do the measurement.
(You only measure the sum of the voltages then... but maybe that would
be enough.)

George H.

Something fancier could alternate the voltages.

But if the 12 volts looks OK, isn't it very probable that the 24 is OK
too?


--

John Larkin Highland Technology, Inc
picosecond timing precision measurement

jlarkin att highlandtechnology dott com
http://www.highlandtechnology.com

 

[George Herold]

On Thursday, April 9, 2020 at 6:20:05 AM UTC-4, blo...@columbus.rr.com wrote:

On Wednesday, April 8, 2020 at 4:25:09 PM UTC-4, John Larkin wrote:
On Wed, 08 Apr 2020 16:00:32 -0400, Steve <nospam@nowhere.org> wrote:

I have been a lurker in this group for some time. This is a totally
non-political post.

I have a remote controlled gate located around 150' from the house. The gate
runs off 24VDC, and the electronics runs off 12VDC. The 12V is being supplied
by a 24V to 12V switching power supply. Right now, I am getting a solid 12V
(measured) from the power supply.

The 24V power is being fed to the gate by 2 #8 wires from a 24V battery-backup
power supply in the house. The voltage drop on these wires is negligible, and I
am getting a solid 24V (measured) at the gate..

I would like to remotely measure both the 24V and 12V at the gate.

Right now, I have a single free wire going between the gate and the house that I
can use without pulling more cable. The wire is now connected to the 24V supply
at the gate, and a voltmeter in the house, but I would like to monitor both the
24V supply and the 12V supply, and don't want to pull more cable between the
house and gate.

Does anyone know of a simple and cheap way to monitor both voltages using only
the one wire? Ground is available through a number of cables, so, ground
reference is not an issue.

Thanks in advance.

Steve

A resistor and a diode could provide you a source that is 24 volts if
unloaded, and drops to 12 when loaded. On the DVM end, the load could
be a resistor and a pushbutton.

Something fancier could alternate the voltages.

But if the 12 volts looks OK, isn't it very probable that the 24 is OK
too?


--

John Larkin Highland Technology, Inc
picosecond timing precision measurement

jlarkin att highlandtechnology dott com
http://www.highlandtechnology.com

Use a resistor divider between 24V and 12V. You should get 18V. Send the 18V back to the hose and set up to comparators in your house to monitor over18V and under 18V

Ahh good. I knew there was at least one difference circuit, but I was
thinking the wrong way.

GH

 

[Phil Hobbs]

On 2020-04-09 09:14, Phil Hobbs wrote:

On 2020-04-08 16:00, Steve wrote:
I have been a lurker in this group for some time.  This is a totally
non-political post.

I have a remote controlled gate located around 150' from the house.
The gate
runs off 24VDC, and the electronics runs off 12VDC.  The 12V is being
supplied
by a 24V to 12V switching power supply.  Right now, I am getting a
solid 12V
(measured) from the power supply.

The 24V power is being fed to the gate by 2 #8 wires from a 24V
battery-backup
power supply in the house.  The voltage drop on these wires is
negligible, and I
am getting a solid 24V (measured) at the gate..

I would like to remotely measure both the 24V and 12V at the gate.

Right now, I have a single free wire going between the gate and the
house that I
can use without pulling more cable.  The wire is now connected to the
24V supply
at the gate, and a voltmeter in the house, but I would like to monitor
both the
24V supply and the 12V supply, and don't want to pull more cable
between the
house and gate.

Does anyone know of a simple and cheap way to monitor both voltages
using only
the one wire?  Ground is available through a number of cables, so, ground
reference is not an issue.

Thanks in advance.

Steve


One approach would be to use a latching 12-V DPST (Form C) relay.
Connect the pole and a 1-uF ceramic cap to the long wire, and connect
the throws to +12 and +24.  Wire the coil as shown.

sense    10k      0----+12V
wire
0----*---RRRR---O
     |           \
    CCC        /  0----+24V
    CCC 10uF /
     |     /
     C   /
     O /
     I
     L
     |
    GND

And on the other end, a couple of pushbuttons and a DVM:

         +24V  S1
          |
          *-> |
              |--
          *-> |
          |
          |
0---------*------------------*
          |     S2           |
          *-> |             DVM
              |--           DVM
          *-> |              |
          |                 GND
         +12V


Push one button for +12, and the other one for +24.  Don't push both at
once.   (To get fancier, you can use a MOM-OFF-MOM toggle switch
instead of the pushbuttons.)

That way, you put a nice beefy pulse on the sense wire that switches the
relay, then after a second or so you can get a good measurement.

Make sure the coil is the right way round--you want a positive pulse to
make it connect to the +24V side.  That way, when it's reading +12 and
you push S1, you put +12V across the coil, and it'll switch to reading
+24.  When you push S2, there's +24V on the cap, so the coil sees a
pulse of -12V and so switches to measuring +12V.  You could also just
ground S2.  That'll overvolt the coil a little going from 24V to 12V,
but that shouldn't hurt anything much.

You may need to experiment with the size of the capacitor.  A 9-volt
relay would get you a bit more margin, which helps when pulling this
sort of stunt.  Obviously this will stop working at some point when the
supply fails or the batteries get too flat.

I once did something like this with two relays so that I could bootstrap
the coil-to-contact capacitance in an ultra-high-Z front end.

Cheers

Phil Hobbs

If you use a 3x Form C (3PDT) relay, you can use the other two sections
to flip the coil around. Then you'd only need one button.

Cheers

Phil Hobbs

--
Dr Philip C D Hobbs
Principal Consultant
ElectroOptical Innovations LLC / Hobbs ElectroOptics
Optics, Electro-optics, Photonics, Analog Electronics
Briarcliff Manor NY 10510

http://electrooptical.net
http://hobbs-eo.com

 

I actually read the responses, here but not there wherever there was.

We have to assume the OPer has a reason for wanting to see both voltages. Why else ?

As such I got an idea. First of all that free wire is not likely to have DC leakage. At least not much. So both the 12 as 24 could go through a resistor, and then diodes, the drop of which would be calculated on the other end.. (there are ways to build this in)

So you take a flip flop, or "bistable multivibrator" and a set of diodes. Each goes through the resistors and then to the collectors of the transistors in the flip flop. Then they go to those diodes. You can get Shottkys if you want or just calculate it, or you oculd just take the meter - to the same diode drop from common and correct it as it sits.

How this "free wire" always sees an open circuit pretty much just going to a meter. Even a panel meter bare is fairly high input resistance. So you have a switch that takes the line to ground/common to trigger the FF outside and get the other reading.

So if for some reason he wants to stay on one setting he can by simply not pressing the button again. Let's say it is peak time and since there are batteries involved it is more important to monitor them. The regulator he has probably has a feedback loop that keeps it constant, so any big changes there do indicate a fault. But at certain times one or the other could be more important.

All the shit costs minimal. Couple transistors, small caps, a dozen resistors tops. A way to build the thing, they got ways for one offs. Those boards that emulate breadboards, five bucks I think for a size that'll probably do three of these.

If automatic switching is desired it is easily put by the user switch. An old style relaxation oscillator would do just fine. It would also facilitate, if desired, showing both by simply multiplexing them.

It is a little unusual I think to refer to such a scheme or DC as that but what other word is there ?

 

[Bill Martin]

On 4/9/20 8:30 AM, George Herold wrote:

On Thursday, April 9, 2020 at 6:20:05 AM UTC-4, blo...@columbus.rr.com wrote:
On Wednesday, April 8, 2020 at 4:25:09 PM UTC-4, John Larkin wrote:
On Wed, 08 Apr 2020 16:00:32 -0400, Steve <nospam@nowhere.org> wrote:

I have been a lurker in this group for some time. This is a totally
non-political post.

I have a remote controlled gate located around 150' from the house. The gate
runs off 24VDC, and the electronics runs off 12VDC. The 12V is being supplied
by a 24V to 12V switching power supply. Right now, I am getting a solid 12V
(measured) from the power supply.

The 24V power is being fed to the gate by 2 #8 wires from a 24V battery-backup
power supply in the house. The voltage drop on these wires is negligible, and I
am getting a solid 24V (measured) at the gate..

I would like to remotely measure both the 24V and 12V at the gate.

Right now, I have a single free wire going between the gate and the house that I
can use without pulling more cable. The wire is now connected to the 24V supply
at the gate, and a voltmeter in the house, but I would like to monitor both the
24V supply and the 12V supply, and don't want to pull more cable between the
house and gate.

Does anyone know of a simple and cheap way to monitor both voltages using only
the one wire? Ground is available through a number of cables, so, ground
reference is not an issue.

Thanks in advance.

Steve

A resistor and a diode could provide you a source that is 24 volts if
unloaded, and drops to 12 when loaded. On the DVM end, the load could
be a resistor and a pushbutton.

Something fancier could alternate the voltages.

But if the 12 volts looks OK, isn't it very probable that the 24 is OK
too?


--

John Larkin Highland Technology, Inc
picosecond timing precision measurement

jlarkin att highlandtechnology dott com
http://www.highlandtechnology.com

Use a resistor divider between 24V and 12V. You should get 18V. Send the 18V back to the hose and set up to comparators in your house to monitor over18V and under 18V

Ahh good. I knew there was at least one difference circuit, but I was
thinking the wrong way.

GH

how would you get >18V for either supply failed? The idea looks
workable, but the compare levels don't look right...
-bill m

 

[ehsjr]

On 4/9/2020 3:19 PM, Bill Martin wrote:

On 4/9/20 8:30 AM, George Herold wrote:
On Thursday, April 9, 2020 at 6:20:05 AM UTC-4, blo...@columbus.rr.com
wrote:
On Wednesday, April 8, 2020 at 4:25:09 PM UTC-4, John Larkin wrote:
On Wed, 08 Apr 2020 16:00:32 -0400, Steve <nospam@nowhere.org> wrote:

I have been a lurker in this group for some time.  This is a totally
non-political post.

I have a remote controlled gate located around 150' from the
house.  The gate
runs off 24VDC, and the electronics runs off 12VDC.  The 12V is
being supplied
by a 24V to 12V switching power supply.  Right now, I am getting a
solid 12V
(measured) from the power supply.

The 24V power is being fed to the gate by 2 #8 wires from a 24V
battery-backup
power supply in the house.  The voltage drop on these wires is
negligible, and I
am getting a solid 24V (measured) at the gate..

I would like to remotely measure both the 24V and 12V at the gate.

Right now, I have a single free wire going between the gate and the
house that I
can use without pulling more cable.  The wire is now connected to
the 24V supply
at the gate, and a voltmeter in the house, but I would like to
monitor both the
24V supply and the 12V supply, and don't want to pull more cable
between the
house and gate.

Does anyone know of a simple and cheap way to monitor both voltages
using only
the one wire?  Ground is available through a number of cables, so,
ground
reference is not an issue.

Thanks in advance.

Steve

A resistor and a diode could provide you a source that is 24 volts if
unloaded, and drops to 12 when loaded. On the DVM end, the load could
be a resistor and a pushbutton.

Something fancier could alternate the voltages.

But if the 12 volts looks OK, isn't it very probable that the 24 is OK
too?


--

John Larkin         Highland Technology, Inc
picosecond timing   precision measurement

jlarkin att highlandtechnology dott com
http://www.highlandtechnology.com

Use a resistor divider between 24V and 12V.  You should get 18V.
Send the 18V back to the hose and set up to comparators in your house
to monitor over18V and under 18V

Ahh good. I knew there was at least one difference circuit, but I was
thinking the wrong way.

GH

how would you get >18V for either supply failed? The idea looks
workable, but the compare levels don't look right...
-bill m

OPEN output failure:
If 12V fails you get 24 volts from the divider;
if 24V fails you get 12 volts from the divider;
if both fail you get 0 volts from the divider.

SHORTED output failure:
If 12V shorts you get 12 volts from the divider;
if 24V shorts you get 6 volts from the divider;
if both fail you get 0 volts from the divider.

If both work, you get 18 volts from the divider.

Unspecified failure = unspecified output from divider.

Ed