So there have been plenty of occasions where I would like to use a switch or even potentiometer in simple circuits I make (just little at home hobbyist creations). But alot of the switches I try to use are very limited on the current they can handle, especially potentiometers. My question is, how can I use switches or pots to interrupt a circuit without running current directly through the switch or pot? Is there a simple solution I'm just not seeing or grasping? Updated to add info Some examples are a homemade benchtop power supply that I would like to add a switch to each rail, but each rail has the ability to output upwards of 50 amps, which not many switches that I've seen can handle. Another example would include trying to add a momentary on push button switch to homemade "hot coil" lighter (the hot coil was a piece of graphite). The push button was rated for 3 amps which I clearly exceeded seeing as how it melted while testing it.

  • \$\begingroup\$ Transistors, relays, SCRs, there are a lot of different possibilities, but we need more information about what exactly you're trying to switch. \$\endgroup\$
    – BeB00
    Aug 5, 2019 at 1:34
  • 1
    \$\begingroup\$ You should also add voltage, AC or DC, type of load (inductive?). It's possible that you should just be using a mosfet like this (digikey.com/product-detail/en/infineon-technologies/…) but 50A is a huge and dangerous amount of current to be switching. Anything in the path with the slightest amount of resistance (like a mosfet) will heat up a lot. The level of knowledge displayed here is worrying because dealing with these sorts of electronics is pretty dangerous. Consider doing more research on the fundamentals before continuing. \$\endgroup\$
    – BeB00
    Aug 5, 2019 at 2:19
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    \$\begingroup\$ use an automotive start relay from a scrap vehicle \$\endgroup\$
    – jsotola
    Aug 5, 2019 at 2:52
  • \$\begingroup\$ Sounds like you are looking for a contactor. \$\endgroup\$
    – Ron Beyer
    Aug 5, 2019 at 3:25
  • \$\begingroup\$ Potentiometers are not switches, nor do they do a similar job. \$\endgroup\$
    – JRE
    Aug 5, 2019 at 10:30

1 Answer 1


All switching circuits will require some current flowing through the switch. It can, however, be kept small so that a miniature switch can control a larger switch rated to connect and disconnect the load.


simulate this circuit – Schematic created using CircuitLab

Figure 1. Simple relay circuits.

Figure 1a shows a simple 12 V relay switching the load. Your switch only has to power the relay coil.

Figure 1b shows how to use a relay to switch multiple power rails simultaneously. In this layout the control circuit is completely isolated from the load power.

Choose the relay coil voltage to suit your control circuit and check that your switch can safely handle the coil current. Select the relay contacts to suit your load voltage and current and make sure that they are DC rated if you are switching DC. Car relays may suit your application as these are common, cheap and switch high current loads (10 A for headlights, for example).


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