Power Supply and NiCd charger

Under construction

Simple power supply and NiCd charger with junk-box components.

Without the enclosure
2SC1105 on left heatsink, LM317 on right heatsink.

PSU:

Output current	Unregulated voltage	Regulated voltage
0 mA	18.8V	12.6V
250 mA	17.2V	12.2V
600 mA	15.8V	11.9V

Charger:

The unregulated part of the PSU is also used for a simple NiCd charger.

[PSU_NiCd_charger2.png]

Charging current is approx. 500mA. This very simple charger has some drawbacks:

No reverse polarity protection.
If the mains is switched off, the battery pack keeps the capacitor voltage at approx. 11V. (A series diode would fix this)
The unregulated voltage is too low. It should be at least 17V @ 500 mA. However the junk-box did not have a suitable transformer. (A 18.5V laptop PSU would be nice). This would also increases the power dissipation of the LM317 when the PSU is in use.
The 3.3 ohm resistor gets hot.

The next version will have reverse polarity protection and will run from a lower supply voltage

Archive containing the Xcircuit files (encapsulated postscript).