Voltage Regulator Constant Heat

**phita23** · 02-13-2005, 10:06 PM

I have this 7805 voltage regulator:
http://www.radioshack.com/product.as...%5Fid=276-1770

I put a piece of aluminum about 2"x2" on the voltage regulator to act as a heatsink.

When my V in (7.5V) and my ground are connected, the voltage regulator produces heat (temperature at least 104F / 40C) , even when V out is not connected.

When V out is connected, it produces slightly more heat.

Is it normal to see the voltage regulator producing heat even if when it's not outputing any current?

Is it safe to put this in the eyeglass compartmet of my car?

**phita23** · 02-14-2005, 02:34 PM

bump

**strohmrs** · 02-14-2005, 03:05 PM

Is the tempurature you stated the heatsink temp or the regulator temp? If that's the regulator temp then you should be ok. The regulator is rated up to 125C. I don't recall them generating any heat without a load on it but 40C is nothing to worry about. Just make sure everything is connected correctly. Left to right with pins facing down: 1-Input, 2-GND and 3-Output. The heatsink should have continuity with the center ground pin and should not be touching any of the pins. As long as the temp with your full load on it is where you said it is, you should be fine mounting it in your sunglass compartment. Just make sure you mount it so that the heatsink and regulator is not touching any plastic or fabric. Leave an air pocket around it so the heatsink will work effectively. If you have metal in there you could use it as an addition heatsink as well.

**jcdillin** · 02-14-2005, 03:16 PM

strohmrs is correct, but mine doesnt put off any heat when it has no load.

**strohmrs** · 02-14-2005, 03:27 PM

If the temp is 40C at the heatsink without a load then he should get a new one. If the regulator has ever been hooked up wrong or has been run very hot or at a high load then it should be replaced. As I said earlier, I don't remember them putting off any heat without a load and with only 7.5V going in there's only about 0.5-1.0V being dissipated as heat. Couldn't hurt to get a new one.

**phita23** · 02-14-2005, 06:07 PM

I've gotten two of them already from radio shack. They both put out a lot of heat.

Do any other local stores offer voltage regulators?

**strohmrs** · 02-14-2005, 06:22 PM

Out of curiosity, what manufacturer is the regulator that Radio Shack sells? There are quite a few companies that make them. I'd try to find a different brand.

**phita23** · 02-14-2005, 08:36 PM

Originally Posted by strohmrs

Out of curiosity, what manufacturer is the regulator that Radio Shack sells? There are quite a few companies that make them. I'd try to find a different brand.

all it says is the info given here
http://www.radioshack.com/product.as...%5Fid=276-1770

**strohmrs** · 02-14-2005, 09:37 PM

It should have some kind of markings on it. They may have a less then ideal batch at your Radio Shack. They work and are within an acceptable temp range while in use. May as well use it for a while and see if it works out.

**kiltjim** · 02-14-2005, 10:52 PM

I work there, and we get them from all manufacturers. All of our ICs come from the cheapest bidder. The one thing I would want to know is if the 7805 you have is made from plastic (sort of) or ceramic. I have seen both, and the plastic, although same ratings and all, gets hotter faster, even with a heat sink.

Just get some from Mouser. You'll pay for shipping, but you could get like 2 dozen of things for what we charge.