Updated 20th December 2010 with photo of cased unit.
In a bid to cut down the number of different boards I have to produce for a wide range of power supplies, I decided to produce a board that would fulfil at least 90% of the types required. The board I present here has the following features:
I’ve also produced 2 versions of the printed circuit board, either with a small on-board mains transformer, or without. Note that in the following board drawings, that only 2 regulators are ever fitted to a board. The reason that 4 are shown is simply so that I wouldn’t have to produce two different PCB designs. (see schematics lower down page)
|Order Code||Specification||Price each (GB Pounds)|
|300-645||Encapsulated Transformer 0 – 6, 0 – 6V (2 x 417mA)||4.43|
|300-655||Encapsulated Transformer 0 – 9, 0 – 9V (2 x 278mA)||4.31|
|300-660||Encapsulated Transformer 0 – 12, 0 – 12V (2 x 209mA)||4.43|
|300-665||Encapsulated Transformer 0 – 15, 0 – 15V (2 x 167mA)||4.43|
|300-670||Encapsulated Transformer 0 – 18, 0 – 18V (2 x 139mA)||4.43|
The Primary Voltage of this ranges is specified as: 0 – 230Vac @ 5.0VA
and the outside dimensions are 44mm X 37mm X 33mm.
I measured these as: 1.75inch X X 1.5inch X 1.25inch
The connecting tags are on a 1.00inch grid. (see circuit board)
Looking at the schematic(s), only 1 set of voltage regulators should be placed on the board, either the fixed (7805,7809 etc) or variable. (LM317) Similarly, the components associated with the variable supply are omitted with a fixed supply.
Variable Voltage version Schematic
|1 amp Fixed Voltage||78XX||79XX||W0..M series (eg ESR 700-151 1.5A/100PIV)|
|2 amp Fixed Voltage||78SXX||79XX (with external power transistor)||KBP series (eg ESR 700-251 2A/100PIV)|
|1 amp Variable Voltage||LM317||LM337||W0..M series (eg ESR 700-151 1.5A/100PIV)|
All fixed resistors 1/4 watt 5%
The 2K2 preset resistors R1 and R2 used to set up the variable voltage version, are standard horizontal mounting.
All electrolytic capacitors – to suit voltage. I suggest 100% over-rating. E.G. Output from transformer 15v ac – capacitor voltage 35 volt.
100nF are disc ceramic 50v working.
LEDs can be of your choosing – adjust R5 and R6 to suit current required.
My friendly Electronics Component Store ESR can supply everything here, including equipment/consumables for the PCBs.
The Completed Boards
Below, a couple of photos showing the completed boards.
A cased 1 amp version in current use is shown. Note the re-cycled hard-disk platters as heatsink for the 2 regulators, giving a distinctly ‘Ritz’ 30’s vibe.
The unadorned schematic is here: http://joebrown.org.uk/images/DualPSU/DualPSU_Shematic.PNG
The Eagle Project for the printed circuit boards is provided in a self-extracting EXE (produced using IExpress) here: http://joebrown.org.uk/images/DualPSU/VersDualSupply.exe