landroversforever Posted December 16, 2012 Share Posted December 16, 2012 Calling the electrical gurus on here.... Mate has given me an old PC screen to use in the truck. The screen takes a 12v input, but I don't know exactly how much its going to like the 12-14v it will get in the car. How can I easily make it a steady 12v? I don't want to have an invertor or a 12v laptop supply as already have the power supply for the netbook (18v I think). Thanks in advance Quote Link to comment Share on other sites More sharing options...
LandyManLuke Posted December 17, 2012 Share Posted December 17, 2012 You need a 12v dc/dc adapter to give you a stable regulated 12v supply. They're commonly used for car PCs. Quote Link to comment Share on other sites More sharing options...
landroversforever Posted December 17, 2012 Author Share Posted December 17, 2012 I will have a search . Cheers. Quote Link to comment Share on other sites More sharing options...
simonr Posted December 17, 2012 Share Posted December 17, 2012 The cheapest solution is to make your own! Determine how much current it requires. My Dell 17" screen says 1.9A @ 12v so yours is unlikely to be much more. Buy a few 7812 Voltage regulators: http://www.ebay.co.uk/itm/L78xx-Serie-Positive-Voltage-Regulator-IC-5V-9V-10V-12V-15V-18V-24V-/200714883555?pt=UK_BOI_Electrical_Components_Supplies_ET&var=&hash=item2ebb8a11e3 As pictured, the pin on the left goes to the vehicle 12v supply. Middle goes to Ground and the right one connects to the screen +ve. With a heat sink (a small 2" square of Aluminium is fine), each of these is good for up to 1 Amp. Parallel up two or more for higher current. The smoothing capacitors are a good idea, but it will work OK without them as the screen will have it's own anyway. An easy way to connect them if you don't have the facility to solder directly is to use the smallest size of connector blocks (Choc Blocks) you can find and screw one pin into each of three blocks then connect wires to the other side. If you find the heat sink gets hot, increase the number of 7812's to increase the current handling capacity. Most of the 5v lighter socket adapters you can buy for charging phones etc just have a 7805 (5v equivalent of the same thing) inside. Si Quote Link to comment Share on other sites More sharing options...
landroversforever Posted December 17, 2012 Author Share Posted December 17, 2012 Cheers Si! I'm up for having a go at making that Just had another look on the screen and it says 12v 3A. Will have a look to see if I can find the voltage reg.s at work Quote Link to comment Share on other sites More sharing options...
landroversforever Posted December 17, 2012 Author Share Posted December 17, 2012 Presumably, without using a heatsink I could just line up more than I need (5?) and use some variboard? Quote Link to comment Share on other sites More sharing options...
CwazyWabbit Posted December 17, 2012 Share Posted December 17, 2012 Just use a heatsink and forget about the veroboard or any kind of circuit board Fixed securely you can then solder solid core wire between the terminals like little buzzbars ...... Quote Link to comment Share on other sites More sharing options...
SORNagain Posted December 17, 2012 Share Posted December 17, 2012 I wouldn't recommend 7812 regulators: At 1A they have a drop out voltage of 2 volts which means that as the input falls to 2 volts above the output they stop regulating.... Buy a switch mode power converter instead. Quote Link to comment Share on other sites More sharing options...
ChrisB Posted December 18, 2012 Share Posted December 18, 2012 This ebay search shows some prebuilt modules which will almost certainly be fine. I use a 5v version for in-car ipad charging (with additional resistors to provide the control voltages) and another for my pi. Quote Link to comment Share on other sites More sharing options...
landroversforever Posted December 18, 2012 Author Share Posted December 18, 2012 I'll make one with the 7812s first, and then see how the voltage output varies. Afterall, the bits are costing me nothing so I have nothing to loose! Quote Link to comment Share on other sites More sharing options...
HoSS Posted December 20, 2012 Share Posted December 20, 2012 7812 will not really do the job, because of the drop. I would use something like this http://www.ebay.co.uk/itm/150657732239?ssPageName=STRK:MEWNX:IT&_trksid=p3984.m1497.l2649 It will give you a stable voltage, no matter if the input is above or below 12v I've used several of these from that supplier and can recommend Quote Link to comment Share on other sites More sharing options...
SORNagain Posted December 20, 2012 Share Posted December 20, 2012 Now that's more like it...I'm going to get one of those myself. Quote Link to comment Share on other sites More sharing options...
SORNagain Posted December 20, 2012 Share Posted December 20, 2012 I'm guessing you didn't buy this one! Not sure how you can heatsink that one to get the full 3A since all the bits are surface mount. Edit:- actually the only thing that other listing does give you is a view of the underside, which shows a plane with loads of vias under the power devices. So a bit of aluminium with heatsink compound against this surface might do the trick. (with suitable insulator!) Quote Link to comment Share on other sites More sharing options...
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