I built this project in February 2004 and it appeared in QSX the monthly newsletter of PEARS. I decided to give it a decal makeover as the 2004 Letraset decals looked rather old and worst for wear.
I know that there are many articles in the past in QSX relating to the above project. However after constructing the Heavy Duty Power Supply described by Andre Botes ZS2ACP in QSX I decided to look at the over voltage protection circuitry.
A thought came to mind that a separate PCB that hosts the over voltage protection components could come in handy especially if you have a power supply with no such protection. I changed the PCB outlay to suit my needs and come up with a board as shown in the image below. (Not to scale) As this is a simple project, I will not go into all the detail to construct the protection unit other than providing you with the component overlay and a few photos of the project amongst the images below.
Just a word of advice: Use thick wire on the input as well as the output side depending on the amount of current (amps) your power supply provides.
This handy little unit could save you a lot of tears and money if your power supply decide to go into over-voltage- or short circuit mode.
Images: (Click on images for larger view)
1. Green LED
2. 1K2 Resistor
4. Relay TAKAMISAWA RY5W-K 5 Volt
5. Push Button
6. BC 108 OR BC 109
7. 1K Resistor
8. 13V Zener Diode
9. 10K Resistor
10. 470 Ohm 5 Watt Resistor
12. 0.0001 Capacitor
13. 0.1 Capacitor
14. 470 Ohm Resistor
15. Red LED
