Post by David Murray on Mar 5, 2008 22:18:30 GMT -5
I'm trying to use a 7805 voltage regulator to get 5V from the 12V system on my car. It seems to get hot pretty fast. I haven't let it stay on more than about 4 minutes and my infrared thermometer is already reading 140 degrees. Not sure how hot it will actually get, or at what point it will burn up. Anyone know? Is there a better way to get 12V (possibly as high as 14V on occasion) down to 5V?
David, you should use a large heat sink with your regulator if you wish to get high currents with large voltage difference. Your regulator must now dissipate to heat the 7V x current. What's your application and current demand?
It's better to get a step-down switcher for the task. I just bought some MC34063-based from Sure Electronics in eBay. These are perfect for the task and don't get hot (and are cheap!).
It is to run some guages in the electric car's instrument cluster.
However.. I think I've found an alternative solution that is very cheap. I went on ebay and bought some car chargers that output to USB for $1.00 (plus $3 shipping) This will probably do what I want even better.
I would use an LM2596 switching regulator. I'm using one to get around 7 volts från 30V. I draw one amp from it, and it's cold to the touch without any heatsink whatsoever. A few more components required though.
Last Edit: Mar 12, 2008 16:13:59 GMT -5 by MadModder