YOU HAVE BEEN WARNED.
This is MK II of my camera flash capacitor bank charger.
Please note this is my first instructible (or as I call 'em Destructible) hence it being in doco format. Tried recording it on video but annoyingly image stabilization made the back ground wobble around while I was working on the enclosure.
- Output Voltage: 240 volts DC
- Output Current: 20mA~
- Max Charging Voltage: Approx 280 volts
- Max Capacitor Bank Size: Infinite, this is due to the use of current limiting resistors. Main limiting factor is your patience.
Originally it was meant to have automatic shut off but because I omitted a capacitor from the output of the bridge rectifier there was way too much ripple current in the circuit. Instead I incorporated a 3.5mm mono socket for connecting an external voltage monitor for when I eventually get around to adding the output filtering capacitor.
The charger as of writing of this article is still a work in progress due to change of plans prior to Christmas.
- Install 250K voltage divider (-/\/\/ 240k \/\/\------/\/\/\ 10k /\/\/\---------) which will scale the output range of 0-500vdc to 0-20vdc for the panel meter.
- Add "Power On" and "Charging" indicators to prevent high voltage surprises.
BoM (Bill of Materials)
All parts were sourced from my local Jaycar :)
- 1x 35A 400V Bridge Rectifier
- 2x 4k7 5w wire wound resistors (20mA current limiting)
- 20v Panel meter
- IEC Socket with incorporated fuse
- Binding posts (Red, Green and Black)
- Normally open button (Start charging)
- Normally closed button (Stop charging)
- 2x DPDT relays, 240vac @ 10A (Latch and Break)
- 3.5mm mono socket
- High grip rubber feet
- Plug back (wallwart for you Americans) transformer (used this because Jaycar wasn't open when I decided to incorporate the relay power into the device)
- 4x M3 x 5mm and 1x M3x15mm
- M205 1A 250vac fuse (for IEC socket)
- 60/40 tin/lead solder
- Reasonable knowledge of electronics, soldering.
- Last but not least a solid garnishing of common sense.
- 3x 10K 1W resistors and 1x 220k 1W resistor for the voltage divider that drives the panel meter.
Total Cost: Approx $150 AUD, note I got some extra stuff such as magnet wire and 20x gator clips for debugging and later on certifying my cap bank.
- Soldering iron/station
- Protective eyewear
- Screw drivers
- Wire strippers
- Side cutters
- Long nose pliers
- Sparky pliers
- Hammer (for cannibalising plug backs for their yummy insides)
- M3 Taping tool
- Label printer
- Blow torch or hot air gun (for heat shrink, don't use a soldering iron, it fouls up the tip)
- Files for working the metal (a Dremel may work but I couldn't be stuffed to get mine out and see)
- Capacitor bank to charge. (See my future instructibles when I get around to building a new camera flash capacitor bank)
How the circuit works:
Basically how it works is it uses the two relays as a latch, SW1 NO "Start" bridges over NO contacts and causes the relay to latch on. RLY2 allows for a remote device to cut off the circuit, SW2 NC "Stop" breaks the loop circuit thus causing to latch to release.
The circuit basically directly rectifies the AC voltage into DC, feeds it through a current limiting resistor and spits it out. Should be noted that there are stupid amounts of ripple that actually cause the circuit to output ABOVE mains potential (e.g. from 220-230vac which is roughly what we see out of our power points (noting this is not RMS) the circuit is able to charge capacitors to 280 volts quite happily then slows down to a mind numbing crawl).
- Some of the photos contain pictures of components that were never used in this project (but at time of taking were intended of being used)