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I have an electrical scooter which has a "Hall Effect Sensor" in the handle-bar, measuring the magnetic flux to determine the amount of "gas" or gauge.

This sensor tends to burn out quite frequently. I replaced it with a potentiometer for a while which worked out great. The only problem is that I can't control it (safely) wearing gloves, and I can't drive in the current temperatures without gloves... So I'd like to give the hall sensor a go again, but add some circuitry to protect it against voltage peaks. I measure 5 Volts across the gnd and "plus" pins. I'm not sure how high the spikes can go, but the serial array of 6x12V batteries delivers more than 80V in total (The 12V Lead-gel batteries actually deliver more than 13V each).

I have found quite some delay-start circuits on Ebay, but they only cover one channel and need a 12V source. I'd need 3 channels (since I don't have a clue what is actually spiking) and I don't have a 12V supply at hand (at least not linked to the switch, bridging one battery would not help).

Adding a capacitor over the sensor might work as a buffer, but it also might decrease it's responsiveness, unless I only apply it to the plus and gnd pins and assume the sensor pin is not spiking.

Adding an extra manual switch would be a last resort, which could also be easily forgotten.

Any other ideas for ways to protect it?

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    \$\begingroup\$ Do you have a datasheet for the hall sensor? \$\endgroup\$
    – jippie
    Dec 5, 2013 at 18:37
  • \$\begingroup\$ @jippie Wish I had, It's got S49EH-242 printed on it and this site seems to be the Chinese manufacturer. Most of their site is Chinese, and I have not succeeded in finding any English data-sheet there. \$\endgroup\$
    – Louis Somers
    Dec 5, 2013 at 18:43
  • \$\begingroup\$ Challenge here is of course that you are guessing about the cause, did you actually observe these power surges? You could take some extra measures to ensure a power surge can't get to the sensor. \$\endgroup\$
    – jippie
    Dec 5, 2013 at 18:51
  • \$\begingroup\$ @jippie, yes it is a guess, but I can't think of any other reason why the hall sensors all die after a few weeks of use? This question is indeed about preventing that surge to get to the sensor, any ideas? \$\endgroup\$
    – Louis Somers
    Dec 5, 2013 at 18:57

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As mentioned in my comment, it feels like guessing what is happening and trying to counter that. Here is a concept to prevent power spikes from getting to the sensor:

schematic

simulate this circuit – Schematic created using CircuitLab

D1 and D2 should be Schottky type, eg BAT43.

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  • \$\begingroup\$ Cool! thanks, I'll give this a shot. I guess the extra 110 ohm resistance will not diminish my "maximum speed", since its quite low compared to the 5K potentiometer I currently use. As you say it's indeed a guess, but if it's not the cause, then the real cause would be a great mystery to me. \$\endgroup\$
    – Louis Somers
    Dec 5, 2013 at 19:33
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    \$\begingroup\$ Just leaving a note on how this worked out. My scooter has been running quite a while now with this solution without any problems. Thanks again. \$\endgroup\$
    – Louis Somers
    Dec 16, 2014 at 19:25

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