mookie Posted February 20, 2008 Report Share Posted February 20, 2008 Hopefully I'm not going to continue to show my ignorance but as some people pointed out in a previous thread I'd made a bit of a misjudgement with regards to my choice of PSU. As a result I've gone back to the drawing board and had an attempt at sketching up a possible PSU. I'm posting the simple schematic here in the hope that someone would be able to check my choice of values as I'm still pretty new at this. The ceramic values I got from the regulator datasheet and the main electrolytic from the guide on diyaudio and the optimised PSU schematic (they seemed to match so I thought it would be a good starting point). Also, is it a better idea to rectify and filter the two voltages seperatly as I planned, or do I gain nothing and would it be more straightforward to rectify once and use a voltage divider to get the two power rails I need.Thankyou for your patience Quote Link to comment Share on other sites More sharing options...
nILS Posted February 20, 2008 Report Share Posted February 20, 2008 You've got some errors in your schem:* You won't be able to generate 12V for 2 reasons:* (1) The input of 6VAC is way too low* (2) the 7809 regulates to 9V not to 12V as the 7812 does* Separate grounds (by using 2 rectifiers) is not really a plus. * The biggest problem is that the 7805 for the cores wants ~7-10VAC and the 7809/7812 want 10-15/13-15V. So one transformer will not really do the trick. Quote Link to comment Share on other sites More sharing options...
mookie Posted February 20, 2008 Author Report Share Posted February 20, 2008 Okay. First lesson, don't draw schematics at half one in the morning.1. Firstly the input is using a 12v centre tapped transformer, that was my reason for using two rectifiers. One will have a 12vac input and the other a 6vac. However with your further remarks I've realised that I'm trying to feed the regulator a value too close to the output. However that can easily be fixed by changing to an 18vac transformer, again centre tapped to give two 9vac windings. (which is handy as there is one sat next to me.2. It's late. I meant 7812The seperate grounds thing. As I've been typing this i'm starting to suspect that that with tapping off the two windings the two grounds will be at different potentials so there is the possibility of some very nasty noises. Ah well. I guess voltage divider is the way to go. Probably simpler too. I'll have another go and get back after I've had some sleep.Thankyou very much nILS.John Quote Link to comment Share on other sites More sharing options...
stryd_one Posted February 20, 2008 Report Share Posted February 20, 2008 Okay. First lesson, don't draw schematics at half one in the morningLOL. Last night Nils got to see me write code at half one in the morning and it was almost as successful ;)I'd highly recommend that you read the thread started by Northernlightx regarding his PSU designs, it's a wealth of information. Quote Link to comment Share on other sites More sharing options...
mookie Posted February 20, 2008 Author Report Share Posted February 20, 2008 My 1o'clock code sin't too bad, but with all the new stuff I'm having to learn with electronics my brain is aching. Thanks for pointing me in the right direction. I'd overlooked the forum with Northenlightsx thread in it and it appears to be just what I need. Sorry for posting in the wrong forum with this thread.Anyway, back to work. Hopefully the next parcel from rapid turns up in the next few hours Quote Link to comment Share on other sites More sharing options...
stryd_one Posted February 21, 2008 Report Share Posted February 21, 2008 Sorry for posting in the wrong forum I hadn't noticed ;) Where should I move this? Quote Link to comment Share on other sites More sharing options...
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