On Jan 21, 9:29 pm, fixitsan <[email protected]> wrote:
> > Don't know why it wouldn't > Tiny..http://f1.grp.yahoofs.com/v1/UCcbT8aqDj-jwP22ddljn4Crlkfwo7hx4zN4nXdT... I got the chance to try this out, crudely, lastnight http://f1.grp.yahoofs.com/v1/UCcbT8aqDj-jwP22ddljn4Crlkfwo7hx4zN4nXdTzN4zcIyip80ZjgtYUZ3IUM3ZW0Vc_fjnEW95-EPpo7Uc3A/%2CIV-17%20based%20project/capheater.JPG Instead of the transistors I switched the side of the heater not connected to the capacitor between 7v and 0V using flyleads and crocodile clips. The heater connection spent most of the time unconnected because it was transiting between connecting with one of the two clips, but even at a rough 8Hz, switched manually, and 150uF of capacitance, with the room lights out I could get the 2.45V filament to glow. By using switching which is almost instantaneous the amount of time spent in between charge and discharge cycles will be greatly reduced and result in better control. The nice thing about the circuit is that if the input pulses stop the filament will not be overloaded because only one charge cycle's worth of energy is stored in the cap at any time, not enough to take out a filament on it's own. A shorted capacitor would be fatal to the heater, unless the heater circuit can operate at full supply voltage. With two 2.45V heaters in series a shorted capacitor would not be fatal, however the RC time constant would double and I wonder if that would become an issue. If using 4 tubes, two paralleled strings of 2 heaters in series will get the RC time back down though. It's something I might try to mess around with some more. If the same pulse train or switching currents could also be used to switch an inductor in circuit, or pass through diodes and caps as if in a voltage multiplier, perhaps a complete supply could be constructed this way ? Chris -- You received this message because you are subscribed to the Google Groups "neonixie-l" group. To post to this group, send an email to [email protected]. To unsubscribe from this group, send email to [email protected]. For more options, visit this group at http://groups.google.com/group/neonixie-l?hl=en-GB.
