Help with LM3914

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Pfrogs

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Hi there,
I have been trying to make a circuit that:

when you turn it ON it lights up 10 LEDs in sequence (1,2,...,9,10) until they are all lit (and stay lit)
And when you turn it OFF they turn off in sequence backwards (10,9,...,2,1) until they are all off (and stay off)

I have come up with this circuit (see attachment). I have tried it in a simulator and all seems to work well. However when I assemble it in mybreadboard, it doesn't light up any LED.

I'm a newby in electronics and I just have a few basic knowledge.

So could someone please help me sort out what might be wrong with my circuit? Our if you have a better ideia for a circuit that makes the effect I want, I would appreciate your suggestions.

Thank you in advanced!
Pfrogs

P.S: I have came across with Popicop post that is exactly what I want to do, but there isn't any circuit that I can have a look at (https://www.electro-tech-online.com/threads/10-led-sequence-light.25342/?highlight=lm3914).
 

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  • LM3914.jpg
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I was actually just working with that part...basically I don't think you need that 20ohm resistor before the leds because their current is controlled by the IC itself.

I imagine this could be done with a decade counter or two...Unsure.
 

Could you send me the Componet info and how you configured the LM3914, I'm new at this too and am also working with a LM3914 project. I've not figured out how to add a componet that's not in my componet bin. Send to TheEquineFencer@AOL.com if you would, thanks.
 
Look at the project I'm working on, https://www.electro-tech-online.com/threads/using-tip42-pnp-paralleled.31927/, scroal down to my drwaing, if you delete the two switches at the top right, J10 and J12 and that whole circuit as well as the OPTOs at the bottom, you can adjust the LEDS from 1-10 from right to left by adjusting the 0-1V voltage you apply at the Vcc O2 input terminal. My guess is you might be able to use a slow charging capacitor or something to do it automatically somehow. I know it works, I'm looking at it now on my shop table.
 
Thank you TheEquineFencer. I have used the basic scheme from LM3914 datasheet which should work, right? I am starting to wondering if it isn't my LM3914 that is malfunctioning. Nevertheless, I will try your scheme to see if it lights up anything.
 
Later tonight, EST in USA if you need it, I can send you some pictures of the PCB as it is assembled. If you send me an e-mail address I can send you some high resolution pictures, you can zoom in and read the numbers and codes on most of the parts as well as see the PCB print on the board .
 
The circuit looks correct but it is missing a supply bypass capacitor. Use 10uF to 100uF from +9V to ground.
The LEDs must be connected with the correct polarity or they won't light.

It uses a linear LM3914 but the capacitor charges and discharges exponentially. The LEDs will light quickly at first then appear to slow down.

If you used an LM3915 logarithmic LED driver then the LEDs would light with equal time between each one.

Of course when the power is turned off then the LEDs will not be powered. Disconnect RV2 to see the LEDs ramp down.
 
Why not just put the on-off spst switch going into the RV2...but always have power going to the leds?

That way as soon as you turn the switch off the input current will go down as the Cap discharges and the led's will still have power to light up until there is no signal anymore.
 
EquineFencer: Thank you for the PCB pic. I have a doubt..what is the "10N" component that is represented in your PCB with a rectangle and connects directly on one side to LM3914-terminal 5 and on the other side to terminal 4? I don't seem to find it in your circuit scheme.

Audioguru: Thank you for your review. I though the bypass capacitor would be optional. Maybe I will go for the LM3915, since what I really wanted is the LEDs to light with equal time between each one. I had checked the LED polarity and that wasn't the problem. Still don't know what is wrong with my circuit.
 

hi, The 10N is a 10nF capacitor, from pin #5 to 0V.

Eric
 

To be honest I have no idea, maybe a capacitor, Here's a picture on the top side with it assembled.
 

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The capacitor marked "10N" on the pcb is marked "103" which is 10,000pF which is 10nF and is also 0.01uF. It is marked "K" which is a tolerance of 10%. It is also marked "100" which is a max voltage of 100V.

ALL electronic circuits need a supply bypass capacitor. It is assumed to be there so is not shown on many datasheets.
 
Hi guys!
Good news! I was finally able to try my circuit with a new LM3914 and it works! So the problem was with my LM3914.
I am sorry to have taken your time with this problem and thank you all for all your help.
 
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