In message <961022151733_1448191733@emout12.mail.aol.com>,
CPattinson@aol.com writes
>About six months ago, Graham Laucht published a circuit diagram for a voltage
>booster - 12>24 volt, I think primarily to drive Turn & Slips. Graham very
>kindly modified the circuit for me so that it would handle a slightly heavier
>current to drive one of my bits of kit.
>I successfully built the unit and it worked well, that is till I tried to
>encapsulate it in resin (some months later). I tried to be clever and used
>Isopon with a minimal quantity of hardener but it exothermed none the less
>and fried the components. The trouble is that although I have the original
>circuit diagram (and original component values), I have lost the revised list
>of components. I seem to recall the values of some resistors and a capacitor
>were changed.
>Graham, if youre out there can you help. I dont have your e- mail address, so
>i've had to go public..
>You may recall it was for a rad alt drawing .6 amp at 24 volts.
OK it's your lucky day Carl and now I know why my 2Gig hard drive is
almost full as here is the original message posted:
In message <960512054729_533451390@emout15.mail.aol.com>,
CPattinson@aol.com writes
>Several months ago someone ( I believe it was Graham Laucht) published a
>circuit design for a 12 - 28 volt converter, to drive a Turn & Slip. I am
>looking for some way of driving a 28 volt radio ( rated at .6 ampere ).
OK here we go nasty ascii time:
Vin +12.5-*------------*-----L1-----*---+D1|---*-------*---Vout +28V
to 15.5V | | | | | 0.6A
| __________________ | |
C1 - + | 5 4 | | C3 - +
- | | R2 > -
| | LM2577T-ADJ | < |
| |-----|1 U1 | > |
| | | 2 |-------| |
| C2- | | > |
| - |_________3________| R3 < |
| | | > |
| > | | |
| R1< | | |
| < | | |
| | | | |
GND-------*---*---------------*----------------*-------*----GND
That wasn't too painful after all!
All parts Maplin references:
R1 1K8 resistor M1K8
R2 43K resistor M43K
Re 2K0 resistor M2K0
C1 10uF 35V Min electro JL05F
C2 470n Min ceramic RA52G
C3 470U 50V High frequency electro JL53H
L1 Newport 14-334-28 330uH Inductor AL23A
D1 2A Ultra fast recovery diode MUR240 GX41U or
Shottky diode (International Rectifier 21DQ04, Motorola 1N5822)
U1 National LM2577T-ADJ Switching regulator
As drawn the output will be a shade under 28V but it makes component
selection easier. Don't substitute C3 for any ordinary electro cap.
Don't substitute C1 for a pill pack tantalum, the CAA doesn't like them.
DI anode shown connected to L1 and U1/4, cathode to R2,C2 and output.
Keep all earth tracks minimal and direct especially C3 to U1/3.
With care it can be constructed on 0.100" pitch stripboard.
Mount in a small diecast box away from any instrumentation and compass.
Feed with breakered or fused supply ~2.0A
Check output with voltmeter into a dummy load first, 47ohm 20W resistor
or two 21W car flasher bulbs wired in series. Switcher transistor (U1)
shouldn't require a heatsink but it could be mounted to the diecast box.
Tab is ground so no need to isolate.
--
Now this time buy some proper low exotherm potting compound from RS or
Maplin! Have fun....
--
Graham E Laucht
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