Resistor help

[Ben]

The GM wiring harness manual indicates that a 5000 ohm- 1/4 watt resistor is needed for the RPM signal.

What I've done is soldered a 4700, followed by three 100's. The four soldered together makes for a rather long chain. Is there a better way to do this, and how should I go about protecting the resistors from being bent?

(LS376/Koso dash)

 

[Will Campbell]

Since you have already soldered these up like that, just cover it all with heat shrink.

If you are careful, after you've applied the heat shrink, folding the resistor string up into quarters will make a smaller overall length.

If you can't find a 5000 ohm resistor, you can probably get by with just the 4700- the calculation for this purpose isn't that stringent.

 

[Alex]

Since you have already soldered these up like that, just cover it all with heat shrink.

If you are careful, after you've applied the heat shrink, folding the resistor string up into quarters will make a smaller overall length.

If you can't find a 5000 ohm resistor, you can probably get by with just the 4700- the calculation for this purpose isn't that stringent.

I tried to it and it didn't pick up the signal.

Like I also said, a single 1/2watt, 1k ohm will work

 

[Will Campbell]

I tried to it and it didn't pick up the signal.

Like I also said, a single 1/2watt, 1k ohm will work

It's a rough estimate. Some Kosos apparently work with no resistor. Some need more. Some can get by with less resistance.

YMMV.

That's what I meant when I said that the calculation was not extremely precise.

 

[Ben]

Since you have already soldered these up like that, just cover it all with heat shrink.

Is there a better way to solder them? The resistors came in packets containing several of them, so I can certainly make up a new chain.

Alex, I didn't discount your advice at all, and truly appreciate your experience. I just don't know if there is a difference between what is needed for the Digi and the Koso.

 

[Nick Montez]

You could wire two 10k resisters in parallel to give the 5k equivalent resistance.

 

[Alex]

Is there a better way to solder them? The resistors came in packets containing several of them, so I can certainly make up a new chain.

Alex, I didn't discount your advice at all, and truly appreciate your experience. I just don't know if there is a difference between what is needed for the Digi and the Koso.

Here's what I would do (infact, this is what I did do ) - buy a crap load of resistors in different amounts. leave your tach wires unconnected. When you do first start, then try different combinations to see what will work. i don't know if the digidash is more sensitive than the kusosososos, but 4700 and 4900 didn't work for me, and I didn't want a gang of resistors, so I was lucky the .5watt 1k worked as ETB (digidash) said it would.

 

[Dimi Terleckyj]

Hi guys

Given that resistors only cost a few cents and are available at any Tandy/Radio Shack store just buy a few in various values and see which one gives you the best result.
As an electronics technician myself I wouldn't waste my time with soldering numbers of resistors together.

Dimi

 

[Darrell]

Hi Ben
Not sure of what or where you are picking up your rpm from so i may be no help, but i have a LS1 in my car and have conected straight from the ECU rpm signel out wire directly to my VDO tach and it works fine.

Darrell
DRB#46
LS1 g50

 

[Grant S]

It been a lot of years since I played with electronic's but has any one checked into, or tried a potentiometer / variable resistor and just dial it in.

 

[Ben]

Nick: I just ran across this statement; "Resistors in parallel half their resistance while doubling their current capability." I used an online calculator and found this statement to be correct. If that doesn't work, I will try using no resistor, and then move to adding them until I find the correct one. I'll post my results to help future builders.

Dazpt: The RPM is coming directly from the GM fuse box. I'm not sure where the box is getting the signal from?

I'm also looking for grounding block suggestions. I know it would be easier, and less expensive to simply bolt the wires to the chassis.

 

[Howard Jones]

Here, 15 cents

RN60D5001FB14 - VISHAY DALE - RESISTOR METAL FILM, 5KOHM, 250mW | Newark Resistors

 

[Nick Montez]

Nick: I just ran across this statement; "Resistors in parallel half their resistance while doubling their current capability." I used an online calculator and found this statement to be correct. If that doesn't work, I will try using no resistor, and then move to adding them until I find the correct one. I'll post my results to help future builders.

It should work fine. I most certainly know my electronics. I'm glad I could help. Seeing your post made me join this forum after 9 months of passively reading.

 

[Doc Todd]

I always hated physics and all the electrical stuff. Now it looks like I'm gonna have to learn it all over again for a good reason!

 

[Doc Kaler]

Welcome Nick and thanks for the tech input!!

 

[Nick Montez]

Welcome Nick and thanks for the tech input!!

No problem. I figured it was about time to put all my schooling to use I've learned quite a bit about cars from everyone on this forum. I hope to build a car when I can find downtime in my Navy career.

 

[Ben]

Thanks Nick, and welcome to the forum. I'm sure that your knowledge will be invaluable around here. The only electrical "training" I've had was when I accidentally cut a live wire in half with a knife. Blew the main breaker in the house, and seriously got my attention. Probably explains a lot doesn't it....:dizzy: