QUASAR PROJECT KIT # 3125 - NEGATIVE ADJUSTABLE POWER SUPPLY MODULE
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DUAL POWER SUPPLIES
Dual power supplies are possible by combining Kit 3125
with Kit 3124. In this case, a transformer with either two
separate output windings or a centre-tapped output are
required. The following diagrams show the input
configuration using these types of transformers.
Using transformer with two output windings
Using transformer with centre-tapped output winding.
The regulators supplied in Kits 3124/3125 are capable of
supplying 1.5A over an input voltage range of 1.2V to
37V. They need at least a 2.5V input-output voltage
differential. In practice the limiting factor on the output
voltage & current will be the power dissipated by the
regulator. For example, if the input voltage is 30V &
PARTS LIST - KIT 3125
Resistors (0.25W, 5%)
330 .................................... R1.................................1
1K ..................................... R2.................................1
10K 10-turn trimpot........... VR1 ..............................1
Capacitors
100nF ceramic ................... C2,4..............................2
2200uF 50V electrolytic ..... C1.................................1
10uF 63V electrolytic......... C3,5..............................2
Semiconductors
1N5403.............................. D1-6 .............................6
LM337T ............................ REG..............................1
3-Terminal Adjustable Regulator, TO-220 case
Miscellaneous
2 way screw terminal ......... X2 ................................2
block
3 way screw terminal ......... X1 ................................1
block
Heatsink for regulator ..............................................1
3mm screw and nut for bolting regulator..................1
to heatsink
3125 PCB................................................................1
the output voltage is 10V and the output current is 1A
then the power dissipated by the heatsink is (30-10)*1 or
20W. This would need a big heatsink. So it is desirable to
keep the input voltage as low as possible to achieve the
required output
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