Strange quirk of the LM3914-1n

[Colin Dawson]

----- Original Message -----
From: "Walter Harley" <walterh@cafewalterNOSPAM.com>
Newsgroups: sci.electronics.design
Sent: Monday, March 29, 2004 10:43 AM
Subject: Re: Strange quirk of the LM3914-1n

"Colin Dawson" <news@cjdawson.com> wrote in message
news:c47h28$2b1$1@sparta.btinternet.com...
I'm sill a little concerned though, having read the data sheet it says
that
there shouldn't be more than 120uA at the Reg Adj pin. According to the
simulation, it says that there is 832.23uA going into this pin. Won't
this
damage the chip? I've already broken several of them and don't really
want
to kill another.

Three principles to understand here.

1. The "120uA max" is not a limit that *you* need to worry about; it's a
promise that the manufacturer is making *to* you. The manufacturer is
promising that the chip won't send more than 120uA out that pin, assuming
you don't do anything unusual. Sort of like input bias current for an
op-amp. How can you tell? Because in the datasheet, it's listed under
"electrical characteristics" rather than "absolute maximum ratings". The
AMR's are the things that you need to observe in order to not blow up the
chip; the EC's are the things that the manufacturer does for you.

Ah, that explains that. I'm kinda getting a little paranoid about these
chips - I've already blown 2 and possibly even 3 (I'm about the test the
third with Fred Bloggs' circuit.

The reason why they specify this is that, if you are using a voltage
divider
on the output, this current results in an error term. See "Internal
Voltage
Reference" on page 7 of the datasheet for details.

I'd read that, but didn't realise that the Electrical Characteristics were
not the same as the Absolute Maximum Ratings.
Think I should dust off my old "L" plates. I've forgotten so must stuff
that I used to know. I'd better refresh myself properly before my next
project... an LED clock linked to the Rugby Time Signal!

2. Generally speaking, putting <1mA through anything won't hurt it. There
are exceptions, but as a rule of thumb, that amount of current is too
small
to worry about.


3. Simulation software is something you have to learn to work with. It
tends to be a bit alarmist. It's worthwhile to pay attention to what it
says; but particularly when it comes to models of IC's, the answers you
get
tend to be a bit different than what happens in the real world. This is
for
two reasons: first, the models are incomplete and imperfect; second, the
software assumes perfect components by default, and in the real world
components are never quite perfect. For instance, a voltage source in
simulation software has zero series resistance unless you specify
otherwise;
but real voltage sources always have some series resistance. And so on.

So, you should look at that 832.23uA and first off read it as "around
800uA"
(because five significant digits is way more than you really have - don't
tell me your power source is exactly 12.000V and you're using .001%
precision resistors); and second off, say "hmm, I wonder why it thinks
that". Sometimes the answer will be "there's something wrong with the
circuit"; sometimes the answer will be "there's something wrong with the
simulation".

I have been reading the simulation as a rough guide. I'm a programmer by
trade, and was trained to C&G
L3 in IT (including Digital Electronics) I realise that the modules
represent the perfect world senario. And even then
there's likley to be errors. It's why I took the time to ask for advice.
Once again, thanks to all that have been kind enough to offer assistance.

Here's goes, Fred Bloggs' circuit is about to come to life..... (or I'm
about to blow another chip)

Regards Colin.

 

[Colin Dawson]

I am mystified over your fixation with this ADJ pin current. Internally
this is the reference voltage for REF OUT. This pin should be GND'd and
it supplies about 80uA typically into GND. That 800uA+ current you
measure sounds suspiciously like a factor 10 error in the simulation
program model- it is nothing to worry about- those people are nothing
but mistakes.

I thought it was a maximum rating on the data sheet. Anyway. I'm about 1/2
way through
putting the circuit on my breadboard. Show be done soon.

Colin.

 

[Colin Dawson]

"Colin Dawson" <news@cjdawson.com> wrote in message
news:c49p1g$da1$1@sparta.btinternet.com...

I am mystified over your fixation with this ADJ pin current. Internally
this is the reference voltage for REF OUT. This pin should be GND'd and
it supplies about 80uA typically into GND. That 800uA+ current you
measure sounds suspiciously like a factor 10 error in the simulation
program model- it is nothing to worry about- those people are nothing
but mistakes.


I thought it was a maximum rating on the data sheet. Anyway. I'm about
1/2
way through
putting the circuit on my breadboard. Show be done soon.

Colin.

That's circuit is brilliant. I've got it running now, with all 10 LED's on,
and the chip is only slightly warm to the touch.
I'm going to stick a heat sink on the chip just to be on the safe side.

Next stage is to make up a PCB that will hold the circuit, it's going to be
split into a display module and a control module. So that I can design the
power box later.

Thanks again for all the help. I couldn't have done this on my own.

Regards

Colin.

 

[Fred Bloggs]

Colin Dawson wrote:

"Colin Dawson" <news@cjdawson.com> wrote in message
news:c49p1g$da1$1@sparta.btinternet.com...

I am mystified over your fixation with this ADJ pin current. Internally
this is the reference voltage for REF OUT. This pin should be GND'd and
it supplies about 80uA typically into GND. That 800uA+ current you
measure sounds suspiciously like a factor 10 error in the simulation
program model- it is nothing to worry about- those people are nothing
but mistakes.


I thought it was a maximum rating on the data sheet. Anyway. I'm about

1/2

way through
putting the circuit on my breadboard. Show be done soon.

Colin.





That's circuit is brilliant. I've got it running now, with all 10 LED's on,
and the chip is only slightly warm to the touch.
I'm going to stick a heat sink on the chip just to be on the safe side.

Next stage is to make up a PCB that will hold the circuit, it's going to be
split into a display module and a control module. So that I can design the
power box later.

Thanks again for all the help. I couldn't have done this on my own.

Regards

Colin.

That is good news, perhaps you missed my earlier suggestion to use the
bargraph for displaying % full power- which is all the same because it
changed. You might want to simulate this one first- the K8004 is
adjusted to run at >1KHz and RV1, RV2 have been set so that 1K pot gives
0-100% duty cycle range- no great amount of precision necessary:
Please view in a fixed-width font such as Courier.


2
Vbatt
HTR Maximum PWR= Pmax = ------
HTR R


ON
Duty cycle= --------= D adjusted by 1K POT and,
ON + OFF


HTR PWR
Average HTR PWR= D x Pmax so that D= ------- or,
Pmax


D= fraction of full power. Therefore it is better


to use LM3914 to display D in place of 1K POT tap.


Q. How to use LM3914 ckt to display D?

A. Use circuit below.




K8004
-----------+
|
|
| HTR
+ o--------------+-----------------o-/\/\/\/\/\/\-o-----+
LOAD | | + - |
G - o----------------+------------------------------------+
N I | | |
D N VREF | | |
-+--+----+----+ | |
| | | +--------+---+ |
| | | | | | |
| v 1K | | / | +-------------|<|--+
+-/\/\--+ | 1K | 1N4148|
D ADJ | / | |
| \ e +-------+----+----|------->LM3914
| | |/ | | | | CKT RHI
1U | +-| | | | |
+---||--+--+ | |\ | | / /
| 0.1U| | | c--+ | 470 1K
+---||--+ / | BC556| | / /
| 5.1K | | | \ \
--- / | | e | |
/// \ | | \| | |
| c | BC556 |--+----+
| |/ | /|
+---+--| | c
| | |\ | | 220K
| | e------+ +--------/\/\--+--> LM3914
| | BC547 | | RF | CKT SIG
| / / / | CF
=== 10K 2.2K 2.2K ===
100n / / / 220n
| \ \ \ |
| | | | |
+---+-----------+-------+--------------+---
|
---
///

Vbatt
Then LM3914 SIG = D x ----- as averaged by RF/CF and
2
Vbatt
LM3914 RHI= ----- so that LM3914 bargraphs D.
2




1K
VBATT>-----------+----|>|--/\/\------\
|10x o |
|LEDs o |
| o 1K |
+----|>|--/\/\------\|
10u | 1K |
+---+------||---+----|>|--/\/\------\|
| | + | |
--- | | |
/// | 100n | LM3914 |
+------||---+ +-------------+ |
| +-+V+ | |
== +-+MODE | |
|470n 270 | | |
CKT RHI >------+-----/\/\----+RHI | /10
| | |
| | |
CKT SIG >--------------------+SIG | |
| | |
| | |
| | |
| | |
| |----+
| |
+--/\/\---+REF |
| 1.5K | |
| | |
+---------+RLO |
| | |
+---------+ADJ |
| | |
| | |
+---------+V- |
| | |
--- +-------------+
///

 

[Colin Dawson]

"Fred Bloggs" <nospam@nospam.com> wrote in message
news:4068A473.7010309@nospam.com...

Colin Dawson wrote:
"Colin Dawson" <news@cjdawson.com> wrote in message
news:c49p1g$da1$1@sparta.btinternet.com...

I am mystified over your fixation with this ADJ pin current. Internally
this is the reference voltage for REF OUT. This pin should be GND'd and
it supplies about 80uA typically into GND. That 800uA+ current you
measure sounds suspiciously like a factor 10 error in the simulation
program model- it is nothing to worry about- those people are nothing
but mistakes.


I thought it was a maximum rating on the data sheet. Anyway. I'm about

1/2

way through
putting the circuit on my breadboard. Show be done soon.

Colin.





That's circuit is brilliant. I've got it running now, with all 10 LED's
on,
and the chip is only slightly warm to the touch.
I'm going to stick a heat sink on the chip just to be on the safe side.

Next stage is to make up a PCB that will hold the circuit, it's going to
be
split into a display module and a control module. So that I can design
the
power box later.

Thanks again for all the help. I couldn't have done this on my own.

Regards

Colin.



That is good news, perhaps you missed my earlier suggestion to use the
bargraph for displaying % full power- which is all the same because it
changed. You might want to simulate this one first- the K8004 is
adjusted to run at >1KHz and RV1, RV2 have been set so that 1K pot gives
0-100% duty cycle range- no great amount of precision necessary:
Please view in a fixed-width font such as Courier.


2
Vbatt
HTR Maximum PWR= Pmax = ------
HTR R


ON
Duty cycle= --------= D adjusted by 1K POT and,
ON + OFF


HTR PWR
Average HTR PWR= D x Pmax so that D= ------- or,
Pmax


D= fraction of full power. Therefore it is better


to use LM3914 to display D in place of 1K POT tap.


Q. How to use LM3914 ckt to display D?

A. Use circuit below.




K8004
-----------+
|
|
| HTR
+ o--------------+-----------------o-/\/\/\/\/\/\-o-----+
LOAD | | + - |
G - o----------------+------------------------------------+
N I | | |
D N VREF | | |
-+--+----+----+ | |
| | | +--------+---+ |
| | | | | | |
| v 1K | | / | +-------------|<|--+
+-/\/\--+ | 1K | 1N4148|
D ADJ | / | |
| \ e +-------+----+----|------->LM3914
| | |/ | | | | CKT RHI
1U | +-| | | | |
+---||--+--+ | |\ | | / /
| 0.1U| | | c--+ | 470 1K
+---||--+ / | BC556| | / /
| 5.1K | | | \ \
--- / | | e | |
/// \ | | \| | |
| c | BC556 |--+----+
| |/ | /|
+---+--| | c
| | |\ | | 220K
| | e------+ +--------/\/\--+--> LM3914
| | BC547 | | RF | CKT SIG
| / / / | CF
=== 10K 2.2K 2.2K ===
100n / / / 220n
| \ \ \ |
| | | | |
+---+-----------+-------+--------------+---
|
---
///

Vbatt
Then LM3914 SIG = D x ----- as averaged by RF/CF and
2
Vbatt
LM3914 RHI= ----- so that LM3914 bargraphs D.
2




1K
VBATT>-----------+----|>|--/\/\------\
|10x o |
|LEDs o |
| o 1K |
+----|>|--/\/\------\|
10u | 1K |
+---+------||---+----|>|--/\/\------\|
| | + | |
--- | | |
/// | 100n | LM3914 |
+------||---+ +-------------+ |
| +-+V+ | |
== +-+MODE | |
|470n 270 | | |
CKT RHI >------+-----/\/\----+RHI | /10
| | |
| | |
CKT SIG >--------------------+SIG | |
| | |
| | |
| | |
| | |
| |----+
| |
+--/\/\---+REF |
| 1.5K | |
| | |
+---------+RLO |
| | |
+---------+ADJ |
| | |
| | |
+---------+V- |
| | |
--- +-------------+
///

I get the idea of what that circuit does. For simplicity, I think it would
be better for me to quit whilst I'm ahead.
I've saved this file, so that I can come back to it later - maybe in a few
months. At the moment it's more important for me to get the circuits built
so that I can finish the box..... At the moment there's a large battery and
a pile of bits sitting in
my living room.

Thanks again for the help

Regards

Colin.

 

[Colin Dawson]

"Fred Bloggs" <nospam@nospam.com> wrote in message
news:406AB374.8040506@nospam.com...

Colin Dawson wrote:
"Fred Bloggs" <nospam@nospam.com> wrote in message
news:4068A473.7010309@nospam.com...


Colin Dawson wrote:

"Colin Dawson" <news@cjdawson.com> wrote in message
news:c49p1g$da1$1@sparta.btinternet.com...


I am mystified over your fixation with this ADJ pin current.
Internally
this is the reference voltage for REF OUT. This pin should be GND'd
and
it supplies about 80uA typically into GND. That 800uA+ current you
measure sounds suspiciously like a factor 10 error in the simulation
program model- it is nothing to worry about- those people are nothing
but mistakes.


I thought it was a maximum rating on the data sheet. Anyway. I'm
about

1/2


way through
putting the circuit on my breadboard. Show be done soon.

Colin.





That's circuit is brilliant. I've got it running now, with all 10
LED's

on,

and the chip is only slightly warm to the touch.
I'm going to stick a heat sink on the chip just to be on the safe side.

Next stage is to make up a PCB that will hold the circuit, it's going
to

be

split into a display module and a control module. So that I can design

the

power box later.

Thanks again for all the help. I couldn't have done this on my own.

Regards

Colin.



That is good news, perhaps you missed my earlier suggestion to use the
bargraph for displaying % full power- which is all the same because it
changed. You might want to simulate this one first- the K8004 is
adjusted to run at >1KHz and RV1, RV2 have been set so that 1K pot gives
0-100% duty cycle range- no great amount of precision necessary:
Please view in a fixed-width font such as Courier.


2
Vbatt
HTR Maximum PWR= Pmax = ------
HTR R


ON
Duty cycle= --------= D adjusted by 1K POT and,
ON + OFF


HTR PWR
Average HTR PWR= D x Pmax so that D= ------- or,
Pmax


D= fraction of full power. Therefore it is better


to use LM3914 to display D in place of 1K POT tap.


Q. How to use LM3914 ckt to display D?

A. Use circuit below.




K8004
-----------+
|
|
| HTR
+ o--------------+-----------------o-/\/\/\/\/\/\-o-----+
LOAD | | + - |
G - o----------------+------------------------------------+
N I | | |
D N VREF | | |
-+--+----+----+ | |
| | | +--------+---+ |
| | | | | | |
| v 1K | | / | +-------------|<|--+
+-/\/\--+ | 1K | 1N4148|
D ADJ | / | |
| \ e +-------+----+----|------->LM3914
| | |/ | | | | CKT RHI
1U | +-| | | | |
+---||--+--+ | |\ | | / /
| 0.1U| | | c--+ | 470 1K
+---||--+ / | BC556| | / /
| 5.1K | | | \ \
--- / | | e | |
/// \ | | \| | |
| c | BC556 |--+----+
| |/ | /|
+---+--| | c
| | |\ | | 220K
| | e------+ +--------/\/\--+--> LM3914
| | BC547 | | RF | CKT SIG
| / / / | CF
=== 10K 2.2K 2.2K ===
100n / / / 220n
| \ \ \ |
| | | | |
+---+-----------+-------+--------------+---
|
---
///

Vbatt
Then LM3914 SIG = D x ----- as averaged by RF/CF and
2
Vbatt
LM3914 RHI= ----- so that LM3914 bargraphs D.
2




1K
VBATT>-----------+----|>|--/\/\------\
|10x o |
|LEDs o |
| o 1K |
+----|>|--/\/\------\|
10u | 1K |
+---+------||---+----|>|--/\/\------\|
| | + | |
--- | | |
/// | 100n | LM3914 |
+------||---+ +-------------+ |
| +-+V+ | |
== +-+MODE | |
|470n 270 | | |
CKT RHI >------+-----/\/\----+RHI | /10
| | |
| | |
CKT SIG >--------------------+SIG | |
| | |
| | |
| | |
| | |
| |----+
| |
+--/\/\---+REF |
| 1.5K | |
| | |
+---------+RLO |
| | |
+---------+ADJ |
| | |
| | |
+---------+V- |
| | |
--- +-------------+
///



I get the idea of what that circuit does. For simplicity, I think it
would
be better for me to quit whilst I'm ahead.
I've saved this file, so that I can come back to it later - maybe in a
few
months. At the moment it's more important for me to get the circuits
built
so that I can finish the box..... At the moment there's a large battery
and
a pile of bits sitting in
my living room.

Thanks again for the help

Regards

Colin.



If you think about your circuit rationally, you will see that it is no
more than an LED dial pointer. There are simpler ways to do this.
Whereas the duty cycle display is more of an actual metric of the heater
state, and heater control is the reason for the project in the first
place -just my $75 worth.

That's why I decided to save the circuit. At the moment, I want to get the
power box up and running. Once I've got a working box and finished the
other projects that I'll want to do, I'll come back to this can upgrade.

Just one question.... I decided to try running the chip in dot mode, but
I'm getting a little problem where the 1st is illuminated at about 1/4 of
normal - how can I stop this?

Regards

Colin.

 

[Colin Dawson]

"Fred Bloggs" <nospam@nospam.com> wrote in message
news:406C1A50.9060909@nospam.com...

Colin Dawson wrote:
"Fred Bloggs" <nospam@nospam.com> wrote in message
news:406AB374.8040506@nospam.com...


Colin Dawson wrote:

"Fred Bloggs" <nospam@nospam.com> wrote in message
news:4068A473.7010309@nospam.com...


Colin Dawson wrote:


"Colin Dawson" <news@cjdawson.com> wrote in message
news:c49p1g$da1$1@sparta.btinternet.com...



I am mystified over your fixation with this ADJ pin current.

Internally

this is the reference voltage for REF OUT. This pin should be GND'd

and

it supplies about 80uA typically into GND. That 800uA+ current you
measure sounds suspiciously like a factor 10 error in the
simulation
program model- it is nothing to worry about- those people are
nothing
but mistakes.


I thought it was a maximum rating on the data sheet. Anyway. I'm

about

1/2



way through
putting the circuit on my breadboard. Show be done soon.

Colin.





That's circuit is brilliant. I've got it running now, with all 10

LED's

on,


and the chip is only slightly warm to the touch.
I'm going to stick a heat sink on the chip just to be on the safe
side.

Next stage is to make up a PCB that will hold the circuit, it's going

to

be


split into a display module and a control module. So that I can
design

the


power box later.

Thanks again for all the help. I couldn't have done this on my own.

Regards

Colin.



That is good news, perhaps you missed my earlier suggestion to use the
bargraph for displaying % full power- which is all the same because it
changed. You might want to simulate this one first- the K8004 is
adjusted to run at >1KHz and RV1, RV2 have been set so that 1K pot
gives
0-100% duty cycle range- no great amount of precision necessary:
Please view in a fixed-width font such as Courier.


2
Vbatt
HTR Maximum PWR= Pmax = ------
HTR R


ON
Duty cycle= --------= D adjusted by 1K POT and,
ON + OFF


HTR PWR
Average HTR PWR= D x Pmax so that D= ------- or,
Pmax


D= fraction of full power. Therefore it is better


to use LM3914 to display D in place of 1K POT tap.


Q. How to use LM3914 ckt to display D?

A. Use circuit below.




K8004
-----------+
|
|
| HTR
+ o--------------+-----------------o-/\/\/\/\/\/\-o-----+
LOAD | | + - |
G - o----------------+------------------------------------+
N I | | |
D N VREF | | |
-+--+----+----+ | |
| | | +--------+---+ |
| | | | | | |
| v 1K | | / | +-------------|<|--+
+-/\/\--+ | 1K | 1N4148|
D ADJ | / | |
| \ e +-------+----+----|------->LM3914
| | |/ | | | | CKT RHI
1U | +-| | | | |
+---||--+--+ | |\ | | / /
| 0.1U| | | c--+ | 470 1K
+---||--+ / | BC556| | / /
| 5.1K | | | \ \
--- / | | e | |
/// \ | | \| | |
| c | BC556 |--+----+
| |/ | /|
+---+--| | c
| | |\ | | 220K
| | e------+ +--------/\/\--+--> LM3914
| | BC547 | | RF | CKT SIG
| / / / | CF
=== 10K 2.2K 2.2K ===
100n / / / 220n
| \ \ \ |
| | | | |
+---+-----------+-------+--------------+---
|
---
///

Vbatt
Then LM3914 SIG = D x ----- as averaged by RF/CF and
2
Vbatt
LM3914 RHI= ----- so that LM3914 bargraphs D.
2




1K
VBATT>-----------+----|>|--/\/\------\
|10x o |
|LEDs o |
| o 1K |
+----|>|--/\/\------\|
10u | 1K |
+---+------||---+----|>|--/\/\------\|
| | + | |
--- | | |
/// | 100n | LM3914 |
+------||---+ +-------------+ |
| +-+V+ | |
== +-+MODE | |
|470n 270 | | |
CKT RHI >------+-----/\/\----+RHI | /10
| | |
| | |
CKT SIG >--------------------+SIG | |
| | |
| | |
| | |
| | |
| |----+
| |
+--/\/\---+REF |
| 1.5K | |
| | |
+---------+RLO |
| | |
+---------+ADJ |
| | |
| | |
+---------+V- |
| | |
--- +-------------+
///



I get the idea of what that circuit does. For simplicity, I think it

would

be better for me to quit whilst I'm ahead.
I've saved this file, so that I can come back to it later - maybe in a

few

months. At the moment it's more important for me to get the circuits

built

so that I can finish the box..... At the moment there's a large battery

and

a pile of bits sitting in
my living room.

Thanks again for the help

Regards

Colin.



If you think about your circuit rationally, you will see that it is no
more than an LED dial pointer. There are simpler ways to do this.
Whereas the duty cycle display is more of an actual metric of the heater
state, and heater control is the reason for the project in the first
place -just my $75 worth.



That's why I decided to save the circuit. At the moment, I want to get
the
power box up and running. Once I've got a working box and finished the
other projects that I'll want to do, I'll come back to this can upgrade.

Just one question.... I decided to try running the chip in dot mode,
but
I'm getting a little problem where the 1st is illuminated at about 1/4
of
normal - how can I stop this?

Regards

Colin.



The least magnitude LED threshold should BE approximately 440mV so that
the 1/4 normal brightness of the LED at minimum 1K pot set means this
threshold is being crossed about 25% of the time- and this is most
likely due to K8004 switching noise. The RHI input is the least filtered
of the two so this is most likely the culprit- and a threshold crossing
here means a negative going spike is being induced- this makes sense
when the k8004 switches a large current inducing a negative going
transient on the VBATT line that drives your circuit. The most expedient
fix is derive the Vbatt source for your LM3914 circuit from the internal
K8004 circuit cathode of D3 diode, and your LM3914 GND is attached to
the DC IN GND terminal. Like so:
Please view in a fixed-width font such as Courier.


Make new tap here -----------+
|
K8004 V
+--------------------------+ +----------+
| D3 | LM3914 | |
(+) >------|---|>|---+----------+-----|-VBATT-->| |
| | | | | |
| C7| +-----+ | | LM3914 |
(+)-L === |SG352|--|--VREF-->| |
External O 100u |CKT | | | CKT |
Vbatt A | +-----+ | | |
(-)-D | | | | | |
| | | +--|--DC IN->| |
| | | | | |
(-) >-----|---------+----------+-----|--GND--->| |
+--------------------------+ +----------+

erm, one slight technical hitch here.... I've not yet attached the K8004
board to the circuit yet! What I've got at the moment is the V+ and GND
connected to the normal power rails on my bread board.

Regards

Colin.

 

[Walter Harley]

"Colin Dawson" <news@cjdawson.com> wrote in message
news:c4kkpt$6sd$1@titan.btinternet.com...

"Fred Bloggs" <nospam@nospam.com> wrote in message
news:406D5C58.9070507@nospam.com...
Colin Dawson wrote:
"Fred Bloggs" <nospam@nospam.com> wrote in message
news:406C1A50.9060909@nospam.com...
Colin Dawson wrote:
"Fred Bloggs" <nospam@nospam.com> wrote in message
news:406AB374.8040506@nospam.com...
Colin Dawson wrote:
"Fred Bloggs" <nospam@nospam.com> wrote in message
news:4068A473.7010309@nospam.com...
Colin Dawson wrote:
"Colin Dawson" <news@cjdawson.com> wrote in message
news:c49p1g$da1$1@sparta.btinternet.com...
[another 300+ multiply-indented lines snipped]

What, are you guys trying for some sort of record or something?

Trust the Internet. Trust Google. You don't need to capture the entire
thread in every message; it'll be there for you. EDIT.

 

[John Woodgate]

I read in sci.electronics.design that Walter Harley
<walterh@cafewalterNOSPAM.com> wrote (in <c4klcv$chl$0@216.39.172.65&gt
about 'Strange quirk of the LM3914-1n', on Fri, 2 Apr 2004:

"Colin Dawson" <news@cjdawson.com> wrote in message
news:c4kkpt$6sd$1@titan.btinternet.com...
"Fred Bloggs" <nospam@nospam.com> wrote in message
news:406D5C58.9070507@nospam.com...
Colin Dawson wrote:
"Fred Bloggs" <nospam@nospam.com> wrote in message
news:406C1A50.9060909@nospam.com...
Colin Dawson wrote:
"Fred Bloggs" <nospam@nospam.com> wrote in message
news:406AB374.8040506@nospam.com...
Colin Dawson wrote:
"Fred Bloggs" <nospam@nospam.com> wrote in message
news:4068A473.7010309@nospam.com...
Colin Dawson wrote:
"Colin Dawson" <news@cjdawson.com> wrote in message
news:c49p1g$da1$1@sparta.btinternet.com...
[another 300+ multiply-indented lines snipped]

What, are you guys trying for some sort of record or something?

Trust the Internet. Trust Google. You don't need to capture the entire
thread in every message; it'll be there for you. EDIT.


Indeed. The text is so long, it dangles out of the bottom of my monitor

and gets tangled in my feet. (;-)
--
Regards, John Woodgate, OOO - Own Opinions Only.
The good news is that nothing is compulsory.
The bad news is that everything is prohibited.
http://www.jmwa.demon.co.uk Also see http://www.isce.org.uk

 

[Colin Dawson]

"Fred Bloggs" <nospam@nospam.com> wrote in message
news:406D5C58.9070507@nospam.com...

Colin Dawson wrote:
"Fred Bloggs" <nospam@nospam.com> wrote in message
news:406C1A50.9060909@nospam.com...


Colin Dawson wrote:

"Fred Bloggs" <nospam@nospam.com> wrote in message
news:406AB374.8040506@nospam.com...


Colin Dawson wrote:


"Fred Bloggs" <nospam@nospam.com> wrote in message
news:4068A473.7010309@nospam.com...



Colin Dawson wrote:



"Colin Dawson" <news@cjdawson.com> wrote in message
news:c49p1g$da1$1@sparta.btinternet.com...




I am mystified over your fixation with this ADJ pin current.

Internally


this is the reference voltage for REF OUT. This pin should be
GND'd

and


it supplies about 80uA typically into GND. That 800uA+ current
you
measure sounds suspiciously like a factor 10 error in the

simulation

program model- it is nothing to worry about- those people are

nothing

but mistakes.


I thought it was a maximum rating on the data sheet. Anyway. I'm

about


1/2




way through
putting the circuit on my breadboard. Show be done soon.

Colin.





That's circuit is brilliant. I've got it running now, with all 10

LED's


on,



and the chip is only slightly warm to the touch.
I'm going to stick a heat sink on the chip just to be on the safe

side.

Next stage is to make up a PCB that will hold the circuit, it's
going

to


be



split into a display module and a control module. So that I can

design

the



power box later.

Thanks again for all the help. I couldn't have done this on my
own.

Regards

Colin.



That is good news, perhaps you missed my earlier suggestion to use
the
bargraph for displaying % full power- which is all the same because
it
changed. You might want to simulate this one first- the K8004 is
adjusted to run at >1KHz and RV1, RV2 have been set so that 1K pot

gives

0-100% duty cycle range- no great amount of precision necessary:
Please view in a fixed-width font such as Courier.


2
Vbatt
HTR Maximum PWR= Pmax = ------
HTR R


ON
Duty cycle= --------= D adjusted by 1K POT and,
ON + OFF


HTR PWR
Average HTR PWR= D x Pmax so that D= ------- or,
Pmax


D= fraction of full power. Therefore it is better


to use LM3914 to display D in place of 1K POT tap.


Q. How to use LM3914 ckt to display D?

A. Use circuit below.




K8004
-----------+
|
|
| HTR
+ o--------------+-----------------o-/\/\/\/\/\/\-o-----+
LOAD | | + - |
G - o----------------+------------------------------------+
N I | | |
D N VREF | | |
-+--+----+----+ | |
| | | +--------+---+ |
| | | | | | |
| v 1K | | / | +-------------|<|--+
+-/\/\--+ | 1K | 1N4148|
D ADJ | / | |
| \ e +-------+----+----|------->LM3914
| | |/ | | | | CKT RHI
1U | +-| | | | |
+---||--+--+ | |\ | | / /
| 0.1U| | | c--+ | 470 1K
+---||--+ / | BC556| | / /
| 5.1K | | | \ \
--- / | | e | |
/// \ | | \| | |
| c | BC556 |--+----+
| |/ | /|
+---+--| | c
| | |\ | | 220K
| | e------+ +--------/\/\--+--> LM3914
| | BC547 | | RF | CKT SIG
| / / / | CF
=== 10K 2.2K 2.2K ===
100n / / / 220n
| \ \ \ |
| | | | |
+---+-----------+-------+--------------+---
|
---
///

Vbatt
Then LM3914 SIG = D x ----- as averaged by RF/CF and
2
Vbatt
LM3914 RHI= ----- so that LM3914 bargraphs D.
2




1K
VBATT>-----------+----|>|--/\/\------\
|10x o |
|LEDs o |
| o 1K |
+----|>|--/\/\------\|
10u | 1K |
+---+------||---+----|>|--/\/\------\|
| | + | |
--- | | |
/// | 100n | LM3914 |
+------||---+ +-------------+ |
| +-+V+ | |
== +-+MODE | |
|470n 270 | | |
CKT RHI >------+-----/\/\----+RHI | /10
| | |
| | |
CKT SIG >--------------------+SIG | |
| | |
| | |
| | |
| | |
| |----+
| |
+--/\/\---+REF |
| 1.5K | |
| | |
+---------+RLO |
| | |
+---------+ADJ |
| | |
| | |
+---------+V- |
| | |
--- +-------------+
///



I get the idea of what that circuit does. For simplicity, I think it

would


be better for me to quit whilst I'm ahead.
I've saved this file, so that I can come back to it later - maybe in
a

few


months. At the moment it's more important for me to get the circuits

built


so that I can finish the box..... At the moment there's a large
battery

and


a pile of bits sitting in
my living room.

Thanks again for the help

Regards

Colin.



If you think about your circuit rationally, you will see that it is no
more than an LED dial pointer. There are simpler ways to do this.
Whereas the duty cycle display is more of an actual metric of the
heater
state, and heater control is the reason for the project in the first
place -just my $75 worth.



That's why I decided to save the circuit. At the moment, I want to get

the

power box up and running. Once I've got a working box and finished the
other projects that I'll want to do, I'll come back to this can
upgrade.

Just one question.... I decided to try running the chip in dot mode,

but

I'm getting a little problem where the 1st is illuminated at about 1/4

of

normal - how can I stop this?

Regards

Colin.



The least magnitude LED threshold should BE approximately 440mV so that
the 1/4 normal brightness of the LED at minimum 1K pot set means this
threshold is being crossed about 25% of the time- and this is most
likely due to K8004 switching noise. The RHI input is the least filtered
of the two so this is most likely the culprit- and a threshold crossing
here means a negative going spike is being induced- this makes sense
when the k8004 switches a large current inducing a negative going
transient on the VBATT line that drives your circuit. The most expedient
fix is derive the Vbatt source for your LM3914 circuit from the internal
K8004 circuit cathode of D3 diode, and your LM3914 GND is attached to
the DC IN GND terminal. Like so:
Please view in a fixed-width font such as Courier.


Make new tap here -----------+
|
K8004 V
+--------------------------+ +----------+
| D3 | LM3914 | |
(+) >------|---|>|---+----------+-----|-VBATT-->| |
| | | | | |
| C7| +-----+ | | LM3914 |
(+)-L === |SG352|--|--VREF-->| |
External O 100u |CKT | | | CKT |
Vbatt A | +-----+ | | |
(-)-D | | | | | |
| | | +--|--DC IN->| |
| | | | | |
(-) >-----|---------+----------+-----|--GND--->| |
+--------------------------+ +----------+



erm, one slight technical hitch here.... I've not yet attached the K8004
board to the circuit yet! What I've got at the moment is the V+ and
GND
connected to the normal power rails on my bread board.

Regards

Colin.



This means you are using a really bad 1K pot with significant resistance
remaining at the stops or you are picking up significant power line
coupling or your power supply is excessively noisy. What are you using
for 5.1V reference if the K8004 is not there? Keep your SIG and RHI
lines to the circuit short and away from anything with power on it. Make
voltmeter measurements.

The might explain things....

Currently, I'm not using the Vref or ground on the K8004, I've got those
lines connected directly to my power rails... therefore it's not 5.1V but
13.9V (since that's what my power supply is delivering. Also as the power
supply is mains driven, I wouldn't be surprised if there is noise on the
line.

As an experiment, I just powered my breadboard directly from my 85Ah Lead
acid battery. It didn't appear to make any difference to the circuit, so at
least I can rule out a noisy power supply. I'd assumed that the Vref was at
12v, I see that that mistake is rather a major blunder. I can see that
doubling the voltage will change the calculations required to make the
circuit work properly. I'm not fussed about doing that, it makes sense that
if the vRef is at 5.1v the sig will be lower, and also the characteristics
of the circuit different. Also I think it might be a nice even be a nice
side effect. The circuit will be used outside at night so if running in dot
mode it's nice to have a base reference so that can be used to determine the
setting.

Regards

Colin.

 

[Colin Dawson]

What, are you guys trying for some sort of record or something?

Trust the Internet. Trust Google. You don't need to capture the entire
thread in every message; it'll be there for you. EDIT.

Damm. missed out on the record again Only about 50 post to go too.

Seriously, though I think I should apoligise to all you guy and gals that
use modems. With a broadband connection it's kinda easy to forget just how
quckly these things can grow. Out of interest how long was it taking to
download?

Regards

Colin.

 

[Walter Harley]

"Colin Dawson" <news@cjdawson.com> wrote in message
news:c4ko0f$buo$1@sparta.btinternet.com...

Seriously, though I think I should apoligise to all you guy and gals that
use modems. With a broadband connection it's kinda easy to forget just
how
quckly these things can grow. Out of interest how long was it taking to
download?

I've got DSL, which is why I read all this nonsense What caught my eye
was the progression of the message sizes. 9k, 10k, 13k, 16k (I don't see
Fred's posts, because he's in my too-much-angry-language file).

16k text for a 33k modem should only take ~5 seconds to download. It's more
the cumulative effect of many such messages... also, in the Google
archives, they show the first 60 or so lines of text and then you have to
click on a link to see the rest. If the first 300 lines are repeats, it's
pretty hard to follow a thread in Google. And yours is a thread that I
expect others in the future might be interested in.

 

[Colin Dawson]

<Major SNIP>

And yours is a thread that I expect others in the future might be
interested in.

Too right, I think that Fred's given out alot of extremely high quality
information in this thread.
I'm sure that there will be other people who want to do the something very
similer. There's loads of variations on the theme.

Regards

Colin.