using a 5v relay with 12v

[Matt]

hello all. I have a simple question. What makes a 5v relay rated at 5v?
Is it limited by the voltage or really by the current? I have a bunch of 5
volt relays that'd I'd like to use with 12 volts. is it possible to add a
small resister in line with the terminals that switch the relay and have it
turn on with a 12 volt supply? They will be one for a while, so I do not
want to risk them heating up too much.

on the other hand, relays are pretty cheap. does it make sense to just get
some proper ones? Either way, I'm curious to know! Thanks!

-matt

 

[Ian Stirling]

In sci.electronics.design Matt <valid@email.com> wrote:
<big snip>

Is it not really feasible to use an RC circuit to delay because of the low
resistance of the coil? sounds like it will take a large capacitance.

It will.
But, it's probably easier than learning the proper way to do it.
(some sort of transistor/IC circuit)

 

[Terry Pinnell]

Ian Stirling <root@mauve.demon.co.uk> wrote:

Time constant is about R*C, so for 2 seconds, you might try 2/500 of a
farad, or .004F (400uF)

No, .004F = 4,000 uF

--
Terry Pinnell
Hobbyist, West Sussex, UK