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I'm using a 6 position 2 pole rotational switch to change the resistance of two input voltages. Each position adds a resistor on each input, thus increasing the overall resistance and lowering the voltages on the outputs, except positions 1/7 which are direct without resistance. This works fine. My problem is that although I'm using high quality Grayhill switches, there's a sweet-spot between positions that causes the voltage to skip to 0R if the knob is turned slowly. If turned fast, its unnoticeable. Is there a simple way to get rid of the spikes between positions? Capacitors in series with each resistor?

switch

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There are two kinds of rotary switches: shorting and non-shorting. Sounds like you've got a non-shorting switch (the switch breaks the current contact before it makes the next one). You need a shorting switch. That will smooth the transitions as the switch makes the next contact before breaking the current one.

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  • \$\begingroup\$ Looks like you're right. I just pulled out my trusty multimeter and carefully turning the knob I can see there's no connection at all in between. Time to pop open the datasheet. \$\endgroup\$ – Fid May 23 '15 at 0:08
  • \$\begingroup\$ Is there a way to temporarily make a NS switch into a S switch before I order the different ones? \$\endgroup\$ – Fid May 23 '15 at 0:18
  • \$\begingroup\$ @Fid - not in general, I'm afraid. You might be able to do some kludgy thing with adding a piece of metal to the wiper, but that, obviously, depends on how the switch is built. \$\endgroup\$ – Pete Becker May 23 '15 at 2:31

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