The idea of this project comes from an old "tradition" of wiring prototypes of PSU on wooden plates, because PCB and others are very inconvenient (particularly for heavy and bulky transformers). I have gathered protection devices in the past but now is the time to put them together in a suitable format !
To be fair it's not really a box, at best an open box, or a wooden drawer. This makes the whole assembly sturdier, and easier to store and move around, without having to reconnect everything, or risky dangling wires.
With a properly protected and controlled mains line, I can safely play with other high voltage devices and design power supplies, in particular for the #YGREC8's relays or the #Power On Sequencer bis.
I hope this inspires DIYers to make their own, or companies to produce them :-)
Initially, the system has 3 parts:
- The input part provides a first protection and isolation from mains. A first circuit breaker trips at about 2A, and also serves as a power switch. The isolation transformer increases safety in case a human touches any contact after the secondary. The ammeter and voltmeter provide a direct feedback while indicating that the mains is connected.
- The second part uses a variac to reduce and dial the output voltage. My variac is rated at 0.8A max but it should be more than enough, but a second set of ammeter and voltmeter are required because they need to be powered from a stable, high voltage (from the variac's primary). The Ammeter can be limited to 1A and have a higher resolution, down to the milliampere.
- The last part is the output stage with a selectable current circuit breaker (to be designed), a safety push button and a wall plug. The variac stage can be bypassed by a switch, and the max. current range is 2A again.
Stay tuned and read the logs for more details !
1. First big progress
2. I need output meters
3. How can I trip the current at arbitrary, adjustable values ?
4. I should have asked eBay first
5. More woodwork
6. First assembly
7. Variac: solved !
8. Incandescent load(s)
9. MainsBox v1.0 ready !
10. Circuit parameters
11. OverCurrent again
12. A proper AC voltmeter ?
13. OverCurrent again again
14. Got NTC
I found this schematic of an electronic fuse that might be of interest
and also this similar one