OT: Need electrical relay for air blower on Christmas decoration

[chuckdallas]

Okay, so I bought a Gemmy "Snoopy Pilot in a Bi-plane" Inflatable Christmas Decoration a few years ago. Finally had enough space in the front yard of the house (versus the balcony of the old condo) to set it up. Had it going great for about a week and then we got a hard rain. Water seeped into the "controller box" which was closed with 4 screws (but no silicone or waterproof sealant). There's a relay inside the "controller box" that blew. I don't want to spend $100-$150 on a new inflatable to get a new air blower, when I can get a new relay for $1 or $3 and solder it back in.

First, I tried to look up the Chinese air blower manufacturer, but their website is in Chinese and I don't read Mandarin very well. I tried emailing Gemmy, but since I didn't do this in June (as I had planned), they are probably EXTREMELY busy filling orders this time of year and haven't written back, and I can't find a phone number to call them.

For you Electrical Engineers or amateur Do-It-Yourselfers, how are relays rated?? The motor is 120 volts and 1.58 amps. There are two other abbreviations on the motor, but I don't recognize them vis-a-vis ratings such as voltage or amperage. I assumed it was a relay, because it's a small 1/2 inch X 1/2 inch rectangle covered in black plastic, connects the electrical cord to the motor, and looks almost exactly like the relay in my RO/DI Autotopoff controller box. I shorted a relay about a year ago and Mr. Autotopoff.com (VERY good guy) sent me a new relay and I soldered the new one back in, so I think I can do the same for the air blower.

What is the purpose of the relay? My Autotopoff relay turned the power to the small pump on or off depending on the float switches in the sump, so I'm guessing it could be the same function for when I turn the power on or off for the air blower. Maybe it just acts as a fuse.

Where can I buy relays? I couldn't find them at Lowes or Home Depot so I think I need a specialty electrical parts store. I'm located in Fort Lauderdale, FL.

[Skipponator]

Radio Shack maybe?

[Hamsternuts]

If you have a Grainger store where you live, they would have them.

Generally, the purpose of a relay is to open or close another circuit by using a small electromagnet. When you hit whatever button is connected to your relay, the small current through the wires coming through the button energizes an electromagnet inside the relay. That magnet pulls on a switch inside the relay and either opens or closes that switch, which is in turn cinnected to whatever device you're trying to turn on or off. The purpose being that the large, heavy gauge wires for the motor dont have to run all the way to the switch and back, which saves cost, hassle and keeps high voltage out of places where you don't want it.

So, there are always 2 pins on the relay that power the elecromagnet switch, which connect to your on/off button or switch. Often, there is more than one switch in a relay, so the other pins are the line(s) in, common, normally open line out, and normally closed line out.

Without holding the thing in my hand, it's kinda hard to tell you how to wire it up. Hope this helps a little bit.

[chuckdallas]

It's not a relay, it's a 9 microfarad capacitor. Went to Radio Shack and bought a small 220 mfd capacitor. Now all I have to do is figure out which of the wires in positive and which is the ground. If I hooked a voltmeter to one of the wires, wouldn't the positive show 120 volts and the negative would be zero?

If I want to connect the cap the correct way, wouldn't the postivie wire be the one that goes into the cap and the ground wire is the "back side" of the cap or would the cap go in line in the postive line?

[Hamsternuts]

A different sized capacitor may not work properly. The motor may not start, might make noise or burn out. What the capacitor is doing is storing a small charge and discharging it slightly out of phase with the incoming AC power. What that does is make it possible to have a rotating magnetic field for the motor to work. The exact timing of this is governed by certain rules with regard to the size of the capacitor. A 9 microfarad cap will not make the same simulated second AC phase as a 220 microfarad capacitor.

[Hamsternuts]

Forgot to mention, you wrote that its a 9 microfarad capacitor, and you bought a 220mfd capacitor to replace it. 9 microfarads would be written as 9 uF and 220 mF would mean 220 milifarads. A huge difference.

As far as hooking one up, generally, AC capacitors are not polarized. And as far as testing it, its a pain with a regular multi meter. An uncharged one will read low resistance and progressively get higher as the meter itself charges the capacitor. And when set to read voltage the meter will read high, and wind down as the meter discharges the capacitor. They do make actual capacitor testing meters.