CharlesElliott Posted June 15, 2008 Share Posted June 15, 2008 I want to run a video camera from the car and need 3.6v. I tried to use a voltage regulator but the heat dissipation required is far too much. I know you can buy convertors from maplin but I'd like to build something specific. How do you convert DC voltage? I'd probably need somewhere between 0.5 and 1A. Charles --- Triple E Racing - build diary and race reports Link to comment Share on other sites More sharing options...
Area Representative Richard Price Posted June 15, 2008 Area Representative Share Posted June 15, 2008 I've made a power supply to power my hard disc recorder to use with a bullet cam. I'm using a voltage regulator and this heat sink to get 5Volts and 2Amps. It's quite adequate, it only gets mildly warm to the touch. Link to comment Share on other sites More sharing options...
Colin Mill Posted June 15, 2008 Share Posted June 15, 2008 You could do it with a switch mode buck regulator. This would be much more efficient than the linear regulator I guess you have tried. There are a lot of ICs designed to do the job that will require a suitable inductor and some caps to complete the circuit. (Here is an example - the MIC4576BT complete with data sheet here) The alternative would be to use a linear regulator (LM317T for example) and arrange a suitable heat sink. With 12v in and 3.6v out you would be looking to get rid of about 8 watts of heat with a 1Amp load. So a 5 degC/watt heatsink would do the job. Edited by - Colin Mill on 15 Jun 2008 18:17:11 Link to comment Share on other sites More sharing options...
CharlesElliott Posted June 15, 2008 Author Share Posted June 15, 2008 thanks guys, will look again at the heatsink option. What do those cheapo convertors from Maplin use then? They certainly don't have a massive heatsink! Charles --- Triple E Racing - build diary and race reports Link to comment Share on other sites More sharing options...
Ian B Posted June 15, 2008 Share Posted June 15, 2008 Simplest way would be to buy a ciggy lead specific to your camcorder, and remove the ciggy plug if you need to Ian - MI 5EVN - Slightly Vider SVelte model 😬 now repainted to match the Autocom headsets (and AA recovery truck 😳) Link to comment Share on other sites More sharing options...
Colin Mill Posted June 16, 2008 Share Posted June 16, 2008 Semiconductors can withstand prolonged operation at up to 150C so some cheap bits of kit make use of this! However, switch mode technology is so cheap these days that they might well use it (PC supplies are switchmode and are all dirt cheap) Link to comment Share on other sites More sharing options...
Roger Ford Posted June 16, 2008 Share Posted June 16, 2008 Not all of them! Link to comment Share on other sites More sharing options...
Colin Mill Posted June 16, 2008 Share Posted June 16, 2008 Well, compared to a 1kW linear its not so expensive - and with that example you are probably paying a 50% premium for the flashy case 😬 Link to comment Share on other sites More sharing options...
jonboylaw Posted June 16, 2008 Share Posted June 16, 2008 Semiconductors can withstand prolonged operation at up to 150C Yikes, that is not what our QA guys tell us... anything over 115c Junction temp in a fine Geo (<130nm) CMOS is definitely a No No for prolonged life... or are we talking power transistors here ? Just buy the correct adapter, it will save you the risk of letting the smoke out your Camcorder! Jon ----------------------------------- Ital or Ford... the choice is yours.... Hmmm, I'll have the ford please Bob. Link to comment Share on other sites More sharing options...
Colin Mill Posted June 16, 2008 Share Posted June 16, 2008 The old wisdom was that dopant migration set in above 150C and the standard sum for bipolar transistors was to calculate heat sinks for a worst case junction temperature not exceeding 150C. Of things I have looked at recently the LM35 temperature sensor ICs are rated up to 150C. Although I wouldn't advocate pushing things (I'm a rather conservative designer by inclination) I suspect there is quite a bit of leeway as a pal of mine, on discovering that a 1N914 signal diode would carry 1 amp, set one up on a bench supply to see how long it lasted. He got bored after about 6 months! Link to comment Share on other sites More sharing options...
jonboylaw Posted June 16, 2008 Share Posted June 16, 2008 Coli9n, Electron migration of the copper interconnect on CMOS is much more of a problem above 115c, so all those uC and processors do not like it hot.. BiPolar power transitors are much hardier so yes 150c may be acceptable. I used to like the reverse polarity electrolytic capacitors on the bench supply, boy they make a pop Jon ----------------------------------- Ital or Ford... the choice is yours.... Hmmm, I'll have the ford please Bob. Link to comment Share on other sites More sharing options...
neil.cavanagh Posted June 16, 2008 Share Posted June 16, 2008 eerrr... I think I'm beyond the knowledge of my 15 years ago B in AS Electronics!! 😬 Though I do remember blowing up capacitors was fun!! *cool* Link to comment Share on other sites More sharing options...
Colin Mill Posted June 16, 2008 Share Posted June 16, 2008 LiPos are rather more fun than the all-too-safe modern vented electrolytics. We set up an old LiPo flight pack in the yard on a long lead to a 20 amp PSU to give it a little overcharge and it did the full Chinese firecracker bit. However, this experiment leaves you with a slightly uncomfortable feeling when holding one (inside a phone) next to your ear 😬 Link to comment Share on other sites More sharing options...
CharlesElliott Posted June 16, 2008 Author Share Posted June 16, 2008 I think I'll buy one of those voltage converters from Maplin 😬. Maybe I'll feed the output of that into a linear regulator to smooth it out.... Charles --- Triple E Racing - build diary and race reports Link to comment Share on other sites More sharing options...
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