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VFD boost supply

by keaster on Wed Dec 26, 2012 3:49 pm

I didn't buy a clock kit I had some IV-11 sitting around and thought I'd build a clock with VFD's. I've build clocks with Nixies before. I came around the 30-60 boost supply here on the site and thought it seemed simple to build, its very similar to the supply I use for my nixies with difference such as lower voltage of course and using a micro controller and not a 555 for the pwm. But I am having a problem, I built it with all the same parts shown on the site, I am using a PIC16F887 @ 8mhz, I have the PWM running at 32500hz with no load I get about 68v but with a load it drops to about 25v...is this normal? I have the tubes multiplexing just before there is any flicker but they are very dim. Is there something I'm doing wrong?
keaster
 
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Joined: Wed Dec 26, 2012 1:29 pm

Re: VFD boost supply

by neutron spin on Wed Dec 26, 2012 11:09 pm

How are you driving the IV-11's?....What device are you using to drive the anode segments...It is really hard to give an intelligent answer on the information provided....Duty cycle in the firmware, filament voltages, etc...Also this forum section is for supported Adafruit products...
neutron spin
 
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Joined: Sat Apr 03, 2010 5:11 pm

Re: VFD boost supply

by keaster on Wed Dec 26, 2012 11:28 pm

Yes I know its for products sold here just looking for a bit of help
I'm using a MAX6921 to drive the tubes the pwm duty is at 80% I've increased and lowered the duty and it doesn't make a difference. I did once make a type o in my code and had 3000hz and not 30000hz and the voltage jump up to about 45 with load and the tube were much brighter. The other thing I tried and don't know how this happened was I had a TIP31C transistor in place of the MOSFET by mistake with the right pwm frequency and the voltage was much higher again. Is there any problems using a transistor in place of a MOSFET?
keaster
 
Posts: 3
Joined: Wed Dec 26, 2012 1:29 pm



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