![]() Or you can sense the inductor current with a current sense resistor on the source of your MOSFET. Whilst inductance tends to be within 10% tolerance, you'll also have to account for power supply variations. Just skimmed your post, and couldn't hold back the need to rant :/ The trouble with using a 555 timer is, the on time should be set depending on your inductance, and power supply. I’ll look into the resources you all sent over and post back with any questions. I want to keep the caps charged up until their charge is needed, but could probably just leave the charging circuit on until that point? Richard Head, station240, & ealex: Thanks for the improved circuit design ideas! I’m all for revising this thing to as optimal as possible. 4) Yeah, I agree a bleeder resistor is a great idea. Rather the Arduino is sending a +3.3V signal (digital OUTPUT pin HIGH) through the diode and resistor to open the transistor and turn on the charging circuit. The D3, Q2, R1 circuit looks upside down because it would be if the 9V supply were headed to the Arduino. 3) The Arduino itself doesn’t connect to the 9V power supply - it’s just switching on the 9V supplied cap charging circuit. If there aren’t any significant disadvantages, it would be nice to overbuild this aspect if the cost difference is negligible. Maybe adding a switch-off mechanism at 250V or so would be safer, though. MK14: 1) I planned to set and limit the charge voltage via the inductor output voltage, or just time the charge cycle so that it won’t have time to charge beyond a certain voltage. They can keep a charge for quite a while (probably minutes (guess, depends on quality of capacitors) or longer, if open circuit). Getting a nasty surprise, after opening it, and accidentally touching the capacitors, while switched off. Yet low enough so that the capacitors get discharged, when switched off, fairly quickly. ![]() It needs to be high enough so that it does NOT load the output too much. It needs about (8.3V - diode drop) or lower to switch the transistor on, from the 3.3V output! (And/or the 1N4004 diode would BLOCK the voltage as well!) (4).You could do with a bleeder/discharge resistor, across the final output. Especially at >=400V (3).How does your Arduino connect to the power supply (9V) ? Because it looks "upside down" to me. But a 1N4004, is NOT the end of the world. 1N4000's are a bit slow for SMPSs as well, but it might be ok, especially at lower frequencies. 1N4007's (1000V, typically same price) might be better (but other diode specs can be worse). (2).The 1N4004 (MIGHT BE FINE, depends on required maximum output voltage) are only just about high enough voltage (400V). By making it switch off when it reaches >= 250V. This could damage them and/or lead to too high a voltage, causing other problems. (1).There does NOT appear to be anything LIMITING the maximum charge voltage, applied to the capacitor bank (C1. I've only had a quick look at your circuit, so could easily have missed things, or be wrong. I've attached a schematic of my current design if anyone feels like taking a crack at it Thanks! I haven't done much math for this yet, just general design, so specific component values are vague at this point. I am relatively new to circuit design, and at best, don't fully understand what I'm talking about some of the time, so I'd like to get some opinions on whether I'm headed in the right direction with this design. The cap-charging power comes from a 9V battery, and the circuit gets switched on by via a transistor connected to an Arduino +3.3V digital output pin. The new design is based around a charge pump, with its MOSFET being driven by a 50/50 duty cycle DC pulse from the output of a 555 timer (with a MOSFET driver in between to assure the MOSFET switching is clean and quick). I'd like to get away from the camera flash circuit because the type of transformer it uses seems very difficult to source. I'm already using these caps as part of a larger project and have been charging them with a cannibalized disposable camera flash cap charging circuit. I'm trying to design a circuit to charge a bank of four 315V/330uf capacitors (hooked up in parallel).
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