Electricians: What rating switch?

[Walker]

I want to install some "mini micro switches" to run my aux. lighting. I will be using a 30amp relay for each individual switch. What is the minimum rating a switch can/should be to activate the relay? I know it doesn't take much but these little switches usually aren't 12v (I think).



I was going to install some larger 12v 25amp (rated) illuminated rocker switches; but have scrapped that idea due to space limitations. Do they make a small pushbutton/illuminated micro switch?

 

[dresslered]

Where you're using relays, you can pretty much get away with just about anything. However, you did use the term "micro" so you better do a rough calculation. Measure the coil resistance of the relay (i. e. 40-ohms). Then divide this number into the supply voltage (say about 13V) and this will give you your minimum current rating of the switch.



13/40 = 0. 325-Amps

 

[fest3er]

Originally posted by Walker

Do they make a small pushbutton/illuminated micro switch?

The short answer is yes. Look at www.microswitch.com (sends you to a Honeywell site. Goto 'Switches' then to

'Pushbuttons (etc. ) near the bottom. Then scroll down a bit and look at the MML 30 Series catalog (700K PDF). It appears this series of switch will handle 1-2A, which should be enough for your needs.



The MML 30 Series measures about 0. 5"H x 0. 8"W x 0. 8"D, which might come close to your definition of 'micro'.



But as dresslered said, do the computation to see what current the relay will draw; that'll determine which model switch you have to use.



Then you have to find a supplier who'll sell 'em to you!



Fest3er

 

[DavesDodge]

Hey Walker-Do as suggested above, then the best place in Alb. to buy the switches is the Electronic Parts Co. on Rhode Island NE. Let me know if you need help putting them in.

 

[Joe G.]

Walker,



Most of these relays draw something like 10ma so you can get away with just about any switch you want. In fact, it would be pretty hard to find a switch that won't work with 10ma.

 

[WTBurke]

Joe G. is correct



Gentelman..... use of basic OHM's law is in order here... .



P= power ... . I= current ... E= voltage... . Hence a relay coil rated at say... 50 mills at 13. 8 volts DC would sink (x) amount of current.



From the above formula P=EI so... . . 50 x 13. 8 = 6. 9 watts... .

Always keep in mind that we are talking "DC" voltage here. AC voltage takes on a very different "peak power" to "average (RMS)" in short "DC" is easy to look at.



So... . all this means is your Micro-switch (u-switch) must be able to "sink" 6 watts of power... . you can than ask your self is this "continuous" (on all the time) or... is it short term (intermittent).



This brings us to "size" of the devices physical demensions... a basic seat of the pants guesstamation is... . any device sinking current un-added by physical-gurth... . can YOU hold it in your hand with out being burned. Example... a small running light at 12 volts drawing 1 amp = 12 watts... . how long can you hold it in your fingers before you drop it... ouch!!!!!!!



Good engeneering (electrical) practice leads one to build at least TWICE the size in current demand so that it will servive and you will never have to fix it... . cause you built it with gusto to begin with



This simple "theroy" of "DC" current goes a long way... .



Best Wishes

William

 

[Walker]

Good info. fellas. I'm going out for the install right now. Wish me luck.

 

[mongoose]

don't forget the pictures when you finish!!!!