Hi, Zapper,
Thanks for the rapid response.
The direct answer is that I want the higher of the two.
The pedal is used in an electric car conversion. The controller is programmed for the Prius two-channel throttle input, but the mfr. said he would reprogram it for a single channel if I sent it back to them. He said that I could still use my existing pedal, but I would have to parallel the two channels, because the controller is still looking for two inputs. There is about .75V difference between the two channels, and the relationship is linear, and there is a 2.5% tolerance, or the controller shuts down. I actually have a channel voltage meter in the car, so I can read the channel voltages constantly, and they read .75V delta at low throttle, going up to .78 delta at high throttle.
The car has an automatic transmission. At "idle" (0 RPM on an electric motor) the tranny pump is not turning.
So when I accelerate, the car "clunks" into gear pretty hard as pump pressure comes up.
I am trying to make the motor "idle." But only when it is in gear...in other words, not in park or neutral.
With no load, the motor would overspeed.
I found a wire coming from the tranny that only grounds in park and neutral, so I can use that to control a relay to turn my "idle" circuit on and off at the appropriate time.
I am not running any motor-driven accessories (air conditioner or power steering pump) so the engine load is pretty constant at idle.
I have determined that 1.4V on channel 1 and 2.15V on channel 2 give me the appropriate idle RPM, whether the tranny is warm or cold.
There are a couple of ways I could achieve this.
One is to just add a couple of variable resistors (voltage dividers) from the 5V supply to the sensor signal, and adjust to the right voltage. Routed through the neutral relay, of course.
A second is to add a couple of Hall-effect sensors to the two channels.
I'm thinking I could just use a second Prius throttle pedal, take the spring out, and rig it as a fixed adjustment lever to feed the idle circuit.
He said that I should parallel the two channels in a single-sensor setup, so obviously one sensor can handle at least .8V difference.
With the reprogramming, I can calibrate the controller to the single channel throttle signal, but I'm wondering what the output would be...the higher voltage, the lower voltage, or somewhere in-between.
Full pedal is 3.6V on the low channel and 4.38V on the high channel.
So at full throttle, if I'm feeding the low channel signal wire 1.4V through the idle circuit, and 3.6V through the throttle circuit, then the idle sensor would need to be able to handle 2.2V of "reverse voltage." The controller manual says that current is 10 milliamps max.
And most of the time, I'm not driving at full throttle anyway.
What say ye? Do you think the output voltage of two paralleled Hall-effect sensors
would be the higher of the two? Or could I at least adjust it to what I want it to be?
I'm sure it couldn't go over 5V, that's supply voltage...
Maybe instead of another Prius pedal, I would have to use independent Hall sensors...
I'm willing to risk damaging the sensors to try it...they're only $40 at junkyards.
Thanks,
--Clipper