Looking for cool Piezo switches for control panel

terrazza · 02-20-2012, 03:29 AM

I'm looking for some really sharp 22 mm on/off switches for my control panel.

I thought the illuminated variety from automation direct looked great, then got my hands on them and they seem cheap and flimsy.

I did some research and found some really cool 22mm anti-vandal switches from the company Langir that are illuminated and only $6 from china. But the LED's on more than half of them have burned out only after 10 minutes of use and testing. They look cool though. Cool Anti Vandal Switches

So, now I'm looking for some solid Piezo type switches. I've seen some pictures of some ones that handle 24 VDC that look awesome and would work out well for my control panel. But I need 120 VAC. Anyone know where I can get a 22mm 120VAC on/off piezo style switch (preferably illuminated) that can handle 1.5 amps? Looking for momentary and latching. Thanks

flatulentfox · 02-20-2012, 03:39 AM

I can't help you as far as piezo switches. Just a question though as far as vandal proof switches: could you possibly be overdriving the LEDs? Most LEDs with no built in resistors can't handle more than 3V or so. LEDs do not handle heat well, and will burn out very quickly if driven to hard.

Just something to check out if you like those switches otherwise.

Good luck!

ruralbrew · 02-20-2012, 07:21 PM

These switches do look cool. But if you look at the technical data for the switches on their web site it says:

"No resistor fitted. An appropriate resistor must be series connected by the user."

terrazza · 02-21-2012, 12:46 AM

Quote:

Originally Posted by ruralbrew

These switches do look cool. But if you look at the technical data for the switches on their web site it says:

"No resistor fitted. An appropriate resistor must be series connected by the user."

Well, I see that now.... So based on the color I see it indicates a voltage range. What resistor would I use in series for let's say the blue LED 120vAC?

**passedpawn** · 02-21-2012, 12:55 AM

Quote:

Originally Posted by terrazza

Well, I see that now.... So based on the color I see it indicates a voltage range. What resistor would I use in series for let's say the blue LED 120vAC?

That's not so easy because of the power requirement.

A blue LED is about 3.5V forward voltage, so you'd need to dirop 117V. Assuming current of 0.02A (typical for single leds), R = V/I = 117 / 0.02 = 5850, or about 6k.

Power dissipation will be V^2 / R or 117^2 / 6000 = 2.3W. Your typical leaded resistor is 0.25W. So, you could twist 10 60k resistors in parallel to make a 2.5W 6kohm resistor. That would work.

[edit] doesn't look like those switches are rated for line voltage

terrazza · 02-21-2012, 04:34 AM

Quote:

Originally Posted by passedpawn

That's not so easy because of the power requirement.

A blue LED is about 3.5V forward voltage, so you'd need to dirop 117V. Assuming current of 0.02A (typical for single leds), R = V/I = 117 / 0.02 = 5850, or about 6k.

Power dissipation will be V^2 / R or 117^2 / 6000 = 2.3W. Your typical leaded resistor is 0.25W. So, you could twist 10 60k resistors in parallel to make a 2.5W 6kohm resistor. That would work.

[edit] doesn't look like those switches are rated for line voltage

Where would I learn more about this, and gather supplies for twisting inline resistors? Radio shack? I guess I assumed it would be rated for inline 120vac voltage....

terrazza · 02-26-2012, 06:17 PM

Would this be a correct schematic for still using the same led switches on 120VAC line?

**passedpawn** · 02-26-2012, 08:23 PM

Quote:

Originally Posted by terrazza

Where would I learn more about this, and gather supplies for twisting inline resistors? Radio shack? I guess I assumed it would be rated for inline 120vac voltage....

I don't think you should run line voltages through that switch.

I learned electronics in college. Don't know what to tell you there. If you have a desire, take a entry course at the local tech school.