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Two Hall-effect sensors in parallel?

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Clipper81

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What would happen if I connect two of the exact same 5VDC Hall-effect throttle position sensors in parallel?
Common grounds, common 5V supply, common signal.

Would the signal just be the higher of the two?
Would one "mess" with the other? Cause interference or something?
Would one damage the other with reverse voltage?

Here is a datasheet on the sensor:
https://evwest.com/support/prius_pedal.pdf

It *is* a dual-channel sensor, but I'm talking about paralleling each channel separately.

There's a specific reason I ask this, but it's a long boring story...

Thanks,
Clipper the Noob
 
It's unclear from the data sheet but, in general you can't parallel two outputs of an electronic device without something bad happening, since they will likely fight each other when they are outputting opposite signals.

You should be able to combine the two signals with some op amps, however. The outputs appear to be differential so you would need to use two op amps configured as differential amps and then sum those in a third op amp. What output do you want, the sum of the two or the higher of the two?

It would appear that the two outputs may be essentially the same signal, they likely just use two for redundancy (safety), so perhaps you don't need to use both signals for your purpose.

Just be aware that, if this is a modification to the car, it could lead to operational failure and a possible accident in the car (which likely wouldn't be covered by insurance due to unauthorized modifications of the car).
 
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
 
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I'm a little confused. Do you want the second Prius throttle controller to output just a fixed voltage to add to the accelerator output? If so, it would seem that just a few resistors could accomplish that.
 
Yes, that's exactly what I'm looking for.
A fixed, minimum voltage on both channels. But only while I'm in gear.
A resistor between the 5V supply that feeds the sensor, and the signal wire?
Probably a pot, so I can adjust it.
 
Do you know, or can you measure, the resistance between each of the two pairs of inputs to the controller?

A pot may work, but if there's a problem getting the right voltage levels then you could use some op amps to sum in the desired offset voltage.
 
You know, I just had a thought.

What if I used a little bitty DC-DC converter, like this one:
https://www.mouser.com/ds/2/330/yev09t03_v5-19301.pdf
They're only eight bucks. I could trim it with a pot.

And I could probably put a diode after it,
to prevent backfeed into the DC-DC converter,
when the throttle circuit voltage is higher than the idle circuit voltage.
Maybe even a Schottkey or germanium diode, for the low voltage drop?

What do you think?
 
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The converter is usually only needed for high current requirements. Those outputs are not isolated so there is little difference between using that and just a resistor from the 12V supply in your applicaiton.
 
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