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logic circuit

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New Member
ok, i need help building a circuit and i though what better place to learn than a place like this.
what i would like to build is a circuit that would control the relays that control the solenoids that shift my auto transmission in my racecar. i would like to have two buttons, one that would shift the car from first, to second, and then to third. The other button would shift it back up in reverse order. all the circuit needs to do is turn on and off the ground to the 2 relays that control the solenoids.
when the car is in first, both relays are grounded
when shifted to second, one relay ground is taken away
when shifted to third, the other relay's ground is taken away
the car upshifts in the reverse order.

my question really is, can this be built?
ps, would be willing to buy or trade if someone would like to build


Gear shift control

I think I may be able to help. There are two ways of doing it - a microcontroller, or discretes.

Is your motor battery 12volts? What is your email address?


New Member
thanks so much for the design, i am currently trying to decipher it using my limited electronic knowledge. i will "shout" if needed, thanks for the offer.
thanks again!


New Member

peter, we have a couple of questions about the circuit for you

1. you put that the diodes should be part number 2N4001, i can only find 1N4001, are they the same?

2. i am getting 1/2 volt resistors, is this ok?

3. do we need to use a seperate power supply, or will our 9.0 to 14.4 volts fused from the battery be suffice.

4. R5, and R6, resistors, does 82K stand for 8.2K ohms?

5. Where do i find 100nf capacitors, digi-key sells only pk and uk?

thanks and sorry for wasting all of your time on silly questions.


Active Member
1) I have not seen the schematic but I would say that 1N4001 is the correct number of diode.
2) Second thing is resistor power dissipation is measured in watts and not volts. So if you are suggested to use 1/2 W resistor don't use any value lower than that or you meay end up blowing them.
4) No 82k does ot mean 8.2k. Instead 8k2 means 8.2k :D



New Member
thanks for the reply, the designer got back to me and the circuit is built and fully functional!
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