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Forum Index : Microcontroller and PC projects : MM power supplies.
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| paceman Guru  Joined: 07/10/2011 Location: AustraliaPosts: 1329 |
I power my MM from a mains powered variable bench supply set at 9v (Manson EP-613 ex Radio Parts) and use the regulated 5v &/or 3.3v supplies from the MM to power: 1. an "always connected" LED indictor board for the MM 20 pin connector and, 2. a solderless breadboard. The bench supply also has separate fixed 12v & 5v outputs which I'm not currently using. I would like to change this and power the breadboard separately since I want to take some load off the MM supplies and be able to experiment with other logic, op-amps and relays on the breadboard - all controlled by the MM. I am building Geoff's mains powered "Utility Power Supply", detailed on his website, which provides fixed 5v & 3.3v along with switchable +/- 9, 12 & 15v supplies which I'll need for +/- supply to op-amps and 12v for relays. My question is: how do I provide the common ground I currently have using the MM supplies for the boards (which previous threads have noted are necessary), if I power the breadboard and auxiliary bits with the other "Utility Supply". Also are there only particular situations when the "common ground" is required? I guess this is probably elementary for a lot of "Back-shedders" but I'm a bit of a newbie at mixing power supplies. Greg |
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bigmik Guru Joined: 20/06/2011 Location: AustraliaPosts: 2914 |
Hi Greg, Assuming I read this correctly, Just link the GNDs together but DON'T link any other Voltages.. Let the Manson drive the MM and the Utility PS drive the add-On PCBs... Just make sure the +5v and +3.3V on the 26 Pin IO header dont connect to the voltages supplied by the Utility PS. Regards, Mick Mick's uMite Stuff can be found >>> HERE (Kindly hosted by Dontronics) <<< |
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| paceman Guru Joined: 07/10/2011 Location: AustraliaPosts: 1329 |
Hi Mick, thanks for your help. Do you mean connect the three GND's (i.e. the connections marked "-") of the Manson outputs and similarly the two fixed GND's of the +3.3v & +5v of the "Utility" supplies? Both the Manson & the Utility mains supply inputs would themselves be powered off the same grounded mains power-board but I guess you don't mean connect them. What about the switchable dual rails (+/- 9,12,15) of the "Utility" supply used for op-amps etc. Are these in effect left sort of "floating"? There shouldn't be any need to connect either of the 26 pin header supply pins to the other board(s), just as long as I can connect the rest of the I/O pins to circuits on them. Also, what about reading analog inputs, either direct to the MM header pins or through IC switches or relays on the other boards. Do I just connect the "-ve" of these to the GND's of the MM or auxiliary boards? Greg |
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BobD Guru Joined: 07/12/2011 Location: AustraliaPosts: 935 |
Greg I looked up your Manson supply. All I can say is wow. I found it for sale at about 80 EUR. Here is the manual for it and a picture. 
If I was doing what you are doing and had the Manson, I would use the Manson as the breadboard supply as its adjustable supply has adjustable current limiting also. This leaves the question of how to power the MM. Altronics offer the plug pack M9237A and Jaycar offer this plug pack MP3310 . I prefer (and use) the Altronics one as it is more foolproof. The Jaycar one is multi voltage and if used incorrectly could cause trouble. From the Manson manual: The grounding of the output terminals is independent so that the output
can be connected in series to make a higher output voltage. Having said all that I am going to leave your questions to Mick. Bob |
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| bigmik Guru Joined: 20/06/2011 Location: AustraliaPosts: 2914 |
Hi Greg, Yes I would suggest ALL GNDs (output GNDs) be connected together, infact they are already in Geoffs Utility PSU.. unless you are looking at a different unit than the one I looked at. The analog inputs are referenced to GND so if all GNDs are at the same referrence then there is no Issue... just make sure the inputs do not go above 3.3V Regards, Mick Mick's uMite Stuff can be found >>> HERE (Kindly hosted by Dontronics) <<< |
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| paceman Guru Joined: 07/10/2011 Location: AustraliaPosts: 1329 |
Hi Bob, I bought it at Radio Spares about 6 months ago for $99 - probably not that good but not too bad either. I'd decided I wanted to get into electronics a bit more and would need a reasonable supply. Would you believe I already had a hardcopy of the Manual(which I did read originally) but I remember that I'd decided at the time that it was pretty minimal (more a safety manual) and I filed it away and forgot it! Re the current limiting - yes I'm sure you're right about it being handy for the breadboard etc but I thought I'd still need the +/- 9,12,15v that Geoff's design gives so I decided I'd build that too (partly for fun as well). That then meant I'd have two good power supplies in front of me but the Manson was the one with the big-ish +9v supply (via the main adjustable supply). I did power the MM for a while with a plug-pack but then decided I'd be wimping out by not using one of my "proper supplies" once I'd finished the "Utility" supply! Hence my questions on this thread. Greg |
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| paceman Guru Joined: 07/10/2011 Location: AustraliaPosts: 1329 |
Yes I could see with Geoff's schematic that the "utility" supply supplies  had a common GND but didn't know what to do about adding the Manson supply. I'd opened up the Manson when I got it to see its innards and found the main adjustable supply was a rather complicated looking switched one and the smaller +5 & +12 outputs were normal regs. That threw me a bit but in hindsight is probably pretty obvious.
That's what I'll do then - I guess the fact that the Manson manual says each supply has a separate GND (unlike Geoff's Utility) doesn't change things? Re the analog inputs - OK thanks for the confirmation, that's what I thought it must be. I've been reading up some electronics books of late so I think I know what to do about making sure any analog inputs don't exceed 3.3v - it's called a voltage divider  Don't bet I won't have more questions though!
Thanks again, Greg |
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