# 5V source, what do you use?



## Matej (Dec 4, 2015)

Hello,
Silly question, but I am curious what you gentlemen use for the 5V supply to the throttle pot box.

I believe my car's ECU feeds 5V to the ICE's throttle position sensor. Would this be a reliable source?

Some/most controllers provide a 5V specifically for the throttle. However, I will be using two controllers controlled by the same pot box, so I would prefer to have a separate 5V source for it.

Do any of you use a 12V to 5V converter for the pot/hall box? This could also come in handy for adding a 5V USB port to the car to power a dash cam with, which I plan to add later.

I appreciate any input.
Thanks.


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## madderscience (Jun 28, 2008)

For a small load (under 1A) which should include any throttle potbox you are likely to see, a simple 7805 regulator circuit (3 pin IC and a couple capacitors) should be fine. that is what I am using and the materials cost only a few dollars. 

One example of many online: http://www.instructables.com/id/78xx-Regulators-Ics/

If you are paranoid, then while fairly unlikely, consider the failure mode(s) of the circuit and how that affects your throttle. It could fail 0V (open circuit) or it could fail 12V (short circuit).


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## Tomdb (Jan 28, 2013)

Your controller should supply the 5 volts for the throttle. You should always have the voltage reference coming from the same thing that will measure it.


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## Matej (Dec 4, 2015)

madderscience said:


> For a small load (under 1A) which should include any throttle potbox you are likely to see, a simple 7805 regulator circuit (3 pin IC and a couple capacitors) should be fine. that is what I am using and the materials cost only a few dollars.
> 
> One example of many online: http://www.instructables.com/id/78xx-Regulators-Ics/


Thank you, that is good information.




Tomdb said:


> Your controller should supply the 5 volts for the throttle. You should always have the voltage reference coming from the same thing that will measure it.


I will be using two controllers, so I would prefer to have them connected identically. The 5V being fed from one controller would probably not have an adverse effect, it is mostly just me being picky.




My car has a mechanical throttle body, but the newer 90's generations used a weird remote mounted mechanically controlled drive-by-wire throttle position sensor (as shown below) before they switched to a fully integrated TPS directly in the accelerator pedal in 2000 or so.

Unfortunately the standalone electronic throttle pedal is not a direct fit, but the remote mounted TPS is easy to retrofit. Would the signal from it be compatible with the controller?


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## CKidder (Dec 12, 2009)

Matej said:


> I will be using two controllers, so I would prefer to have them connected identically. The 5V being fed from one controller would probably not have an adverse effect, it is mostly just me being picky.


Depending on the controllers it might be possible to connect the 5V sources and grounds together between the two controllers. Some DC/DC converters can be paralleled this way. That would cause both systems to be tied together. Then the throttle signal could go to both as well. But, I'm kind of leery of the idea. They might not like being paralleled, the throttle value might read differently between the two controllers, its hard to say. I really wouldn't use two controllers both connected to the same throttle. Generally one controller gets the throttle signal and then the second controller is a slave that does what the first controller says to do. A master/slave relationship between controllers is safer as you know they're going to be on the same page.



> My car has a mechanical throttle body, but the newer 90's generations used a weird remote mounted mechanically controlled drive-by-wire throttle position sensor (as shown below) before they switched to a fully integrated TPS directly in the accelerator pedal in 2000 or so.
> 
> Unfortunately the standalone electronic throttle pedal is not a direct fit, but the remote mounted TPS is easy to retrofit. Would the signal from it be compatible with the controller?


I don't see why not. It depends on what that TPS module is and what sort of throttles the controller supports. But, generally throttle signals work one of two ways - they output a varying voltage or they output a signal over CAN. In the first case there are two basic types - potentiometer and hall effect. Pot throttles work by varying resistance and thus the resistance of the output changes as you press the throttle. Hall effect just basically changes the output voltage and always has a moderately high resistance. But, usually they're interchangeable. CAN output, on the other hand, is a totally different thing. That's like getting the throttle value sent to you over a serial port. It's totally not the same thing at all. Some controllers support that, some don't. I'm going to guess that a 90's car did not have a CAN throttle though. So, chances are you could make it work.


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## WolfTronix (Feb 8, 2016)

CKidder said:


> Depending on the controllers it might be possible to connect the 5V sources and grounds together between the two controllers.


I would recommend that you diode OR the separate 5V supplies with a two schottky diodes.

That way if one controller comes up before the other (or shuts down before the other), it is not back feeding power into the other controller.


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## frodus (Apr 12, 2008)

For a one throttle to two controllers, connect the wiper of each to the wiper of the pot, the ground of both to the pot, and only ONE 5V supply to the pot. The ground reference is really what you need to ensure you have. Don't try to use diodes or connect the two 5V supplies.


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