Minimum switch current

Thread Starter


Joined Jan 18, 2008
Is there a minimum switch current to ensure reliable switching for toggle and push button switches?

I am thinking of using a switch in a delay circuit with a comparator. The more current I design for, the bigger the capacitor I will need. Since the target delay is 0.5 to 1 sec. the capacitor size is not trivial on an SMD PCB with a 1 mA current. Put another way, any opinions on whether a 100 uA current is too low for a mechanical switch.

Some relay specifications give a minimum current, but I could not find such a specification for the toggle switches (CK, E-Switch, Tyco) I reviewed. My thinking is that switches have a different mechanical action that might lead to much lower minimum currents.

Thanks. John


Joined Apr 20, 2004
There is no minimum current that has to flow through the contacts on a switch. The significant figure is the contact resistance, typically in milliohms. If there is a difference in potential, current will pass through the switch.


Joined Dec 20, 2007
A low current or no current switch has gold-plated contacts. They have a max power rating of about 2W. They are called a DRY contact. they cost the same or slightly more than silver plated contacts. I use them as audio switches.

Silver contacts tarnish and don't work at low or no currents. They rely on a high power spark to burn away the tarnish.

Thread Starter


Joined Jan 18, 2008
Thanks for the great advice. I will use a switch with gold contacts. What gave me pause was the datasheet for some Tyco relays:

Contact Data
Arrangements: 1 Form A (SPST-NO) Wiring Diagram Code 1, 2,3.
2 Form A (DPST-NO) Wiring Diagram Code 5.
1 Form C (SPDT) Wiring Diagram Code 1, 2, 3.
2 Form C (DPDT) Wiring Diagram Code 5.
Material: Silver-nickel 90/10.
Minimum Load: 12V/100mA.
Expected Mechanical Life: 10 million operations.
Initial Contact Resistance: 100 milliohms max @ 1A 12VDC.

When I saw that minimum load, I thought I would never be able to match that. So, it started me wondering if there was a similar minimum for switches.

A 100K resistor at 12V into 10 uF will do just fine and still have some current. John