Magura throttle to servo tester failsafe?

Hi
A safetyissue ive experienced by trying to disconnect the throttle from my servotester/esc setup.
I first stumbled upon it when riding in rain and I guess it affected either the pot itself in the throttle or the anderson connectors I use for it.
What happens in both cases is a fast ramp up of throttle.

What would be the easiest way to invert this behavior. So that throttlesignal problems results in decreased throttle?

The non electrical and "more reliable but not very clever" solution would be to just have a pot in a waterproof compartment with the rest of the electronics and have a mechanical connection to the throttlehandle.
Seems clumsy tho, and I would prefer the stuff being more intelligent to completely eliminate the possibility of uncontrolled throttle increases.

perhaps get a better quality throttle like a 'domino' for eg that should be more waterproof.

Wheazel said:

Hi
A safetyissue ive experienced by trying to disconnect the throttle...
...when riding in rain and I guess it affected either the pot itself in the throttle or the anderson connectors I use for it.
What happens in both cases is a fast ramp up of throttle.

What would be the easiest way to invert this behavior. So that throttlesignal problems results in decreased throttle?

Click to expand...

You have two distinct failure modes:

1. disconnecting the throttle
2. water incursion causing a WOT condition (although the exact failure point (throttle or connectors) is unknown)

These appear to be side effects of using an RC test device as a throttle converter - it simply lacks the circuitry that you might otherwise expect in a vehicle controller - certainly for the first case anyway. These failures don't particularly have anything to do with the Magura - unplugging any pot from the tester will leave it to misbehave in the same fashion.

• For the first case, you can try adding a pulldown resistor across the wiper and ZERO throttle pin (probably Gnd). Something like 68K-100K should work fine. This should be on the tester board itself so that it becomes a reliable built-in feature of the PCB - safe from any possibility of disconnect due to throttle wiring failures. This should pull the tester input to ZERO throttle with nothing connected. It employs only a very small current that will easily be overpowered by normal throttle operation. This is a standard practice on conventional ebike controllers.
  
  
• The second case is similar in effect to a common throttle failure - loss of the Gnd connection. This causes the wiper or 'sense' input of the controller to be pulled high by the (still connected) +5v throttle connection. Some controllers handle this by shutting down on an 'input fault' when the throttle voltage exceeds a voltage above the normal max throttle voltage (e.g. 4.5V). This detection requires some extra logic in the controller which your tester lacks. Any throttle will fail this way from loss of Gnd or water in connectors pulling the sense wire high. Since you have the same wiring vulnerability as all throttles, don't know for certain if the water incursion was in the Magura, but do know that you were using unsealed Andersons for throttle connection, I would recommend just sealing up the throttle connection to address the known shortfall and re-evaluate the situation if you have another failure episode.

In the end, no amount of waterproofing can address common mechanical wiring/connector failures that cause input fault WOT runaways - this requires smarter electronics.

If you have the money and are looking for monitoring of current/voltage/speed/temperature (and other features) you might consider a CA V3 to replace your servo tester - it has a native throttle-voltage-to-PWM operating mode as well as throttle input fault detection. This should get you much closer to the failsafe operation you request.