RC car question?

[Shockwave]

I've been working on a homebrew remote control car for my friends grandson and have run into a unique problem. It's a 52 volt ,13 cell battery, powering a 750 watt brushless motor.

The issue relates to the RC throttle control that currently operates a servo to turn the hall effect throttle. This mechanical link has added more latency and play than desired and we'd like to replace it electronically.

We thought we found the right interface board to convert the output signal of the RC receiver, to the output voltage of the old hall effect sensor, but it's not producing a DC output above 1.3 volts and it should be 5.

To make matters more complicated, we are learning there are differences between some of the digital input signals these boards work with. For example, do I need one that takes a PWM or PPM input from the RC receiver? Do we have any RC experts able to share some advice?

 

[nomadradio]

Odds are your servos are PPM. Sounds as if the interface board isn't listening for that control format, maybe?

A glance with with a 'scope would reveal if the interface is really producing a steady DC output, or a pulse train. If so, this will explain the low DC voltage reading.

Did the old hall-effect control really deliver a steady DC voltage to contol the motor controller? I'm not terribly up to date on modern-day motor controllers.

73

 

[w9cll]

I have been in the R/C hobby for over forty years now..Servos are ppm but over the last few years everything I is going optical now. While I don't do cars on my.planes I use on (sometime two) servos on each control surface. You should be able to make an electronic connection or depending on the size of the car just use two.servos, one for.each wheel and mix them together on the TX.

 

[unit_399]

Shockwave -
You might find this application note useful for designing a circuit that eliminates the mechanical linkage.

https://www.nxp.com/docs/en/application-note/AN4776.pdf

- 399