switches and relays

[RGRAT1618]

I am looking for a good place to buy switches and relays. I am a firefighter and need to make a custom switch pannel for my light bar and strobes. Thanks for the help.





Rob

 

[Cooker]

Whatever you do, use Bosch relays. I have had way too many of the cheapo relays fail. The cheap ones will obviously work fine, but they don't seem to last as long.



Sorry I don't know of an online souce as I get mine locally.



-Ryan

 

[klenger]

You might check WW Grainer.



http://www.grainger.com/

 

[merryman]

the wrecking yard

When I was in a wreking yard looking for a normally open vacume switch, I noticed all the fuse and relay panels in vehicles; thinking ahead, I took a couple small fuse panels and a couple small panels of relays (neatest one was a covered panel of about five relays from a Geo), together with the vacume switch, I think the wrecker charged me $10. 00. Mounted a small fuse and a small relay panel under the hood and have taped various accys. through them.



Vaughn

 

[Dkevdog]

I get most of stuff locally, but Galls is a great source for stuff like that. Excellent service too.



Kev

 

[bigkavr]

As much as I hate to admit it, Radio Shack has one of the best relays on the market up to 30A. I've used numerous ones and RS

has the best for the money. IMO

For switches, I've had my best luck with industrial type rocker switches. I get mine at Lowes. A word of warning though, you might NOT want to use the self illuminating switches. Since they

need an internal ground, they're more likely to blow fuses if the switch starts going bad. (Radio Shack switches are noted for this... )

I build switch boxes for fellow firefighters and use various sized

plastic project boxes that I get at RS. (cheap, but strong. . ) Everything is relayed with dual power coming from the battery.

Instead of illuminating switches, I use indicator lights beside the

switches, much easer to see. If I can help you in any way, feel free to e-mail me direct. -- email address removed --

 

[BK]

the Bosch relays are great and worth the money if you can find them. the RS relays are cheaper - knock offs of them. I've used them too without failures.



Both are rated 30Adc, inductive load. Which is important. There's a high inrush when you turn on a lamp. Lesser relays will arc their contacts closed or just blow the their contact out after a few cycles.



Also you should add a diode to each relay coil, any 1 amp/200V diode is fine. It's wired across the coil. Banded end to +. When you turn off the relay the magnetic field collapses and induces a negative voltage, the diode will clamp this. These pesky induced voltages, if not clamped can find common mode paths and play bad tricks on the electronics in the trucks. I know others will say that they've never had a problem, and if all things are just right, you may not have a problem. There's no way for you to be sure. These negative induced voltage spikes can also peck away at the susbstraites of the IC in you electronics. . so they maynot fail today, but might fail a year from now. Real cheap insurance.



Bob

 

[bigkavr]

BK,



You are correct sir... I bow to the electronic guru. : )

I've noticed that by using indicator lamps with the switches,

the "backfeed" is absorbed by the lamps. Not nearly as

electronicaly correct as the diodes but it works. Also, my power

supplies always come direct from the battery. (properly fused

of course... ) I always thought this would prevent any unwanted

spikes or inductions from causing any harm. Am I thinking wrong

on this one?? Always willing to learn. : ) Thanks.

 

[BK]

Single point grounds and single point Voltage source is a good thing, if you can do it.



I always run "home runs" to the battery and fuse them there.

Single point or home runs help to prevent possible over loading of a circuit and current loops if you not sure whats really up with that circuit that you've tapped off of. There are just some things the battery cant do, hence why you can buy filters to get ride of if certain noises that are carried via the 12v eletrical system that the battery just cant filter out.



Using the indicator to absorb the voltage is a bit iffy as you suggested, but could work if the impedance is low enough and the inductive characteristic doesnt inhibit the current flow, acting like a limiting resistor, raising the absolute clamp voltage.

Most IC's are designed to accept no more than . 6 - 1V of negative input. A diode will generally be . 6V or less, depending on the current. LED (has indicator lights) do not like reverse voltages and arent tolerant to them. Plus their bias resistor guarantees a higher clamp voltage, not soo good.



So being a purist (and a believer and follower of Murphy... Rule # 1654 = If I dont put the protective device in, the event will happen and kill what the protective deviece was there to protect. After you then fix the destroyed item and add the protective device, the said event will never happen again)

and since it's real cheap I add the diode.



Bob

 

[mongoose]

when looking for switches to use in my overhead console i found many types and sizes of switches at these two sites. both sent a free catalog too.



http://www.digi-key.com/



http://www.mouser.com



i bought my small rockers at digi-key.



I have not ever heard of using a diode for the relays. Will have to add some to mine as i saw the other led's blip a little this morning when it was dark and i turned the high idle off.

 

[BK]

Mongoose,



your right one...

both Digi-Key and Mouser are very popular companies with the engineering crowd. Good places, good companies. I've ordered tons and tons of stuff from Digikey over the last 20 years. . like anyplace, rarely they screw up, but they take care of it if they do.







Bob

 

[Great White]

check these people out

I live near Los Angeles and have found relays and switches for my projects at: http://www.allelectronics.com/ order their catalog. They have the plug in adapters for the Bosch, Omron, Zettler and others. The prices are good, product is first quality.



Checked the part #s SRLY-6, Relay Socket

RLY-404, Relay

I have both in my truck and they work perfectly. AND the socket comes with the diode already installed.

Rich

 

[RGRAT1618]

Thanks for all the help, I ordered a few catalogs. I started to build the pannel out of 2024 t-6 allum. now just need switches and relays. thanks again for all the help.



Rob