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| ne555 nixie power supply not working |
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| Boschi:
so, i have a few days off uni and i want to finally use some nixie that i have laying around for quite sometime. first thing first: a power supply. i tryed to use all parts that i had laying around, so i used this schematic with a few changes: https://www.ledsales.com.au/kits/nixie_supply.pdf the only changes that i did was to use a apt13003sztr instead of the irf740 and add a resistor of around 100 ohm in order to limit the base current, but is not working. the yellow trace is the pin 3 of the 555, while the purple one is between the transistor, the coil and the diode (also, i detached the hv output capacitor after the diode in order to see more clearly what is going on on the output side). any suggestion about what is going wrong? |
| malagas_on_fire:
Well i would recomend first check the connections within the schematic and instead of drive directly the mosfet should be using a 1k to 10K resistor to drop the voltage a little bit on the gate since 555 and mosfet share the same voltage rail , thus the voltage in the gate must be lower than the source. |
| Boschi:
the apt13003sztr is a NPN, i didnt specify it clearly before. also, im not concerned about the connections because the ne555 is oscillating, the problem is in the output stage and i already checked there. |
| spec:
+ Boschi Neat, nixi tube power supply. :) Can you explain what exactly is happening when the circuit is fully wired up with the high voltage capacitor fitted? The first thing to do is fit a low loss capacitor between the power supply pins of the 555: 1uF would be good. It is always wise to check the power lines with a scope, to ensure they are the correct voltage and free from drop outs. Were the only changes to substitute the IRF740 for an APT130035, or are there any other changes? The peak current into the 100uH inductor at a switching frequency of 45kHz, and a voltage of 9V, is around 1A and you are asking a lot of the APTI130035 to supply that current (its current gain would only be 5 at the most and you are exceeding the safe operating area I would guess). Also, is the 100uA inductor rated at 1A and is it a high frequency type? Is the inductor rated at 200V, at least? Is the diode a 1A , at least, high speed type, like the UF4004, or is it an ordinary 1N4004? Is the high voltage output capacitor a high frequency type or just an ordinary aluminum electrolytic type? Just some thoughts :) |
| MasterT:
I experimented with nixie boost converter last summer, and came to conclusion: BJT is too Slow and can't replace MOSFET. I tried MJE13003 & 2N5551. You can easy spot slow reaction on a scope, rising edge of the purple line must be 100-300 nanosec right after yellow line falling edge. Not like 1- 5 usec, you may get with BJT. Later I find an explanation to this in DS, look here: Storage Time with Resistive Load ts — — 3 us Fall Time with Resistive Load tf — — 0.5 us And compare to Turn-off delay time td(off) - 70 - ns Fall time tf - 20 - ns https://www.mouser.ca/ProductDetail/?qs=W0yvOO0ixfFGjdM3IlgsHw%3d%3d - MOSFET I was using. I was able to get 800V out of 5V input, and diodes should be also as fast as mosfet, 20 nsec or better. FR107 or MUR160 |
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