Another lm2917 thread

Thread Starter

propertyco

Joined Nov 8, 2022
14
This is the circuit from the spec sheet that matches your setup. Additional signal conditioning as Ian0 suggested maybe required. The component values should be right on for 1.75 volts at 117hz.
View attachment 282700
Progress. After realizing they flip-flopped 12 and 11 on that diagram...

That circuit works on my bench using tone generator and headphone cables

In the car it immediately blew the lm2917, checked the diode I'm using for clamping and it clamps at 32v while the input max is 28v, not sure if the 10k resistor on the input would've dropped the voltage enough.

I'll look into the clamping circuits provided above along with others

Thanks everyone.
 

Thread Starter

propertyco

Joined Nov 8, 2022
14
Corrected link

Current issue I have lol

At idle or any rpm under 2k it will not move the needle.

I'm amazed I'm having such problems with a simple circuit.

I appreciate everyone's help!
 
Last edited:

Thread Starter

propertyco

Joined Nov 8, 2022
14
Did you use the same component values shown on the schematic.
I still don't understand what you meant about the pin11 and pin12 flip flop.
Yes 100% the same as the diagram

They're flipped in order.
They have the right components on them, and labeled correctly, but visually they're flip flopped
 

sghioto

Joined Dec 31, 2017
5,379
Have you tried adjusting the needle?
I saw a YouTube video that describes how to fix such a problem that appears to have the same issue as your meter.
Search under "Tach meter needle adjustment".
 
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