12V Leisure Battery status using 2x LM3914s

[chemelec]

Breadboarding it up with your Schematic, It does NOT WORK.
The First 3914 works, but the Second 3914 Does Not Work.

Joining Pins 4 & 8 Together on the Second 3914, allows it to Work, BUT it will NOT Adjust Correctly as Alex recommended it should.
And when LED's Above LED 10 are On, LED 10 Also Stay Lit up.

Resistors: 1/4 watt resistors are OK.
That PNP transistor is OK.
As to that CAPACITOR, Not sure on Correct Value, and until the Circuit Works to test it, there is no way to know what is the best value or type.

 

[alec_t]

A Good Quality, "Low Leakeage" cap across R2 should do that. (Try 100uF)

It would need more than that, because with your circuit when the main switch goes off so does the LED supply.

I notice PNP9 and PNP10 are shown with the e/c connections reversed in your schematic.

Missing connections? Do you mean the 20k resistor which goes somewhere... between pin 10 an 11 on the 1st IC.
What else have I missed?

The 20k (22k is probably easier to source) is missing and the dot-carry connection is not shown correctly.

Pin 1 of each IC behaves differently from the other LED-driving pins, so to enable Dot-mode the transistor driver stages for LEDs 1 and 11 need to be different from the drivers for the other LEDs.
Here's a revised schematic which provides both Bar and Dot modes (switch-selectable). Note that pin 11 of U1 has the pull-up 22k resistor to +V and also connects to a LED driver stage. The values of R7 and R10 are a compromise between allowing sufficient 'on' LED current in LED1 and LED11 and minimising the spurious 'off' LED current.


Edit: This revision should overcome the points chemelec noted with your version.

 

[chemelec]

Presently I was testing this Just in Dot Mode.
Also I am Not using the Driver Transistors as that is Redundant so far as Calibration goes.

 

[garynobles]

Ok, so silly mistake with the transistors sorted, well spotted!
I have bridged R2 with C1, whatever the value this should slow the turn on/off of the lights right?

C2 is on the LED power source, so the LEDs will drain this for power when turned off.

So in this case would 100uF for C1 be ok? I have no idea about C2's value.

Also rather than a dpdt switch I am using jumpers, I wont be changing mode when it is on, and i will probably stay with BAR mode unless the drain is a big issue.

How is it looking?

Chemelec, if you still have it bread boarded would this solution work?

As for the 20k resistor I can source it from the same place, might get 2 months for the to get it though :-( (along with all the other resistor values!)

2 months might give me the time to finish my PhD and not get distracted by electrical projects!

Gary

 

[alec_t]

I have bridged R2 with C1, whatever the value this should slow the turn on/off of the lights right?

It's part of the solution.

C2 is on the LED power source, so the LEDs will drain this for power when turned off.

You have C2 in series with the LED supply. That's not going to work.
Here's how I'd do it:-

So in this case would 100uF for C1 be ok?

That will give you ~ .25 sec ramp-up/down time. I think you'd find a longer period would be prettier .

How is it looking?

You still don't have the dot-carry connection from U1 pin 9 to U2 pin1, so the dot mode won't work properly (LED10 will stay on).
The drivers for LED1 and LED11 haven't been changed so the internal auxiliary current source at pins 1 of both ICs will keep LEDs 1 and 11 permanently on.

 

[chemelec]

Still can't get it to Calibrate correctly.

20K is a standard value.
At least in Canada.

Sorry Going out Shopping and also out for supper Today.
So no more time today.

 

[garynobles]

Thanks for trying chemelec

So back to the diagram, pin 1 [IC1] to 9 [IC2] connected - forgot that one!
I think I have added the Mosfet as you indicated, the dummy resistor confused me a little, did I get it right?

So no C2 needed?

I will now google up on the Mosfet to see what it does, im sure ive used one years ago...

thanks

Gary

 

[alec_t]

pin 1 [IC1] to 9 [IC2] connected

No. Pin 9 (IC1) should go to pin 1 (IC2).

I think I have added the Mosfet as you indicated

I only indicated it symbolically. The dummy resistor is just that: a dummy (representing the majority of the voltmeter components), so it was only for simulation purposes. The FET drain (upper terminal in the schematic) replaces the Ground connection of everything except Vbat, R1, R2, C1, M1. The FET is being used to switch on/off the whole circuit. The +V supply of the circuit should remain permanently connected to the battery Vbat to be monitored. When the button is pressed C1 charges up slowly via R1. When its voltage reaches the FET gate turn-on threshold (a few volts) the FET turns on. At 11.8V LED1 turns on, followed by other LEDs in sequence as it continues charging. When the button is released the LEDs turn off in reverse sequence as C1 discharges (more) slowly through R2. Then the FET turns off when the C1 voltage has dropped below the turn-on threshold.

So no C2 needed?

No.
BTW you still don't have the different drivers for LED1 and LED11, and switch S2 is wrongly placed .

@chemelec

Still can't get it to Calibrate correctly.

It won't if you have U2 pins 4 and 8 connected as stated above.

 

[chemelec]

@chemelec

Still can't get it to Calibrate correctly.
It won't if you have U2 pins 4 and 8 connected as stated above.

With No Connection between pins 4 and 8 on IC2, I Can't get Any of the LED's on IC2 to light.

 

[alec_t]

@chemelec

With No Connection between pins 4 and 8 on IC2, I Can't get Any of the LED's on IC2 to light.

Do you have Rhi(IC1) linked to Rlo(IC2) and the 'In' signal going to both pins 5?
If the 3914 resistor dividers are close to the 'typical' 12k as per spec then the trimmers should allow these target settings:-
Rhi(IC2) = 9.79V,
Rlo(IC2) = Rhi(IC1) =9.32V
Rlo(IC1) = 8.85V

What values are you getting? If they're not as above then the bottom resistors (R4, R6 in my schematic) will need changing.

 

[alec_t]

If it helps, here's the schematic showing the FET connection:-

 

[chemelec]

Sorry, Found the Problem.
One BAD Contact on my Old Breadboard.

 

[garynobles]

Hi,

So some diodes and two 10k resistors, I will amend my diagram after the weekend. Then I will start sourcing the right components

Gary

 

[garynobles]

Phew, heat wave here!

Anyway, here is the latest circuit diagram, I have sorted out the problem with the pins 9 and 1 and the MOSFET and added more resistors and some diodes as you showed.

Is this diagram now correct for the Sparkfun circular led ring?

The laser cut parts have arrived in the UK and I will pick them up from my parents when I pass through Dorset, I hope to also pick up all the components too!

Thanks again

Gary

 

[alec_t]

Is this diagram now correct for the Sparkfun circular led ring?

Looks ok now.

Dorset

Brings back my childhood memories. Lived in Bournemouth area.

 

[garynobles]

Thanks, if you don't mind I will create a list of components for you to check over before I buy them.

I went to Uni in Bournemouth, I also worked in Swansea, now in the Netherlands!

Gary

 

[alec_t]

Here's the list:

 

[garynobles]

Well it looks like my last post didn't post... 16 diodes? a typo?

 

[garynobles]

I have a question about the MOSFET
I looked up the one suggested and it has 6 pins, this was the closest I could find:

https://uk.farnell.com/jsp/search/productdetail.jsp?sku=2212876

In my circuit the MOSFET only has 3 pins. Is the circuit right or component right?

Thanks

Gary

 

[garynobles]

Would this one do the job?
https://uk.farnell.com/on-semiconductor/bs170g/mosfet-n-to-92/dp/9556192