Electronic circuit to convert 0.8-4.2 to 0-5 VDC

[KrisKasprzak]

I have a DC motor controller that requires a 0-5 VDC input to vary the PWM for a DC motor controller. I bought a motorcycle-style handgrip to control the controller. Unfortuntatly the handgrip is based on a 49E hall sensor and outputs 0.8 to 4.2 VDC. Meaning the controller will never shut the motor off, or drive to full on.

My main requirement is that the throttle must be spring loaded to automatically turn off if the hand is removed.

I'm guessing I can build a simple circuit with an OP-AMP to bias the signal down, then amplify it up to get an output of 0-5. Maybe there is another way, but I'm not sure. Or maybe someone knows of a throttle that is potentiometer based?

Here's where you come in...if such conversion is possible, anyone wanna draw up a schematic?

Thanks in advance.


Link to controller

SyRen 50A regenerative motor driver - analog, R/C, and serial motor control

Link to throttle

https://www.amazon.com/dp/B07H5MGFML?ref=ppx_yo2ov_dt_b_product_details&th=1

 

[luni]

Looks like the controller has a simple serial interface (set speed by sending a byte). So, instead of an EE solution you could think of using a Teensy (or a cheap controller like a XIAO) to read in the throttle value, calculate the required speed from it and send it to the motor controller. They claim a max speed update rate of 2kHz which seems to be plenty.

 

[PaulStoffregen]

anyone wanna draw up a schematic?

Sure, here's a quick attempt

 

[bicycleguy]

Nice, didn’t know you were an opAmp nurd too!

 

[KrisKasprzak]

Thanks Paul. I'll give it a try.

 

[MarkT]

Simpler symmetrical method, no LM4040 needed:

I picked the AD8656 because I know its properly rail-to-rail on the inputs and outputs, cheaper options exist. Decoupling cap omitted, it is not optional though.