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Registered Member #579
Joined: Mon Mar 12 2007, 09:45AM
Location: Burntwood, Staffs, England
Posts: 46
I have tried to do this lots of times - and I did have one working in a fashion once I have a nice flyback driver set up with NE555 and two paralleled Mosfets It works well and is silent with 30 mm arc The audio is neg rail and nO5 pin on the Ne55 via a 474 cap I also have a 0,01 cap to ground - decouple I can not get a peep out of it Do I need a lot of volts to drive pin 5 on the timer chip? Do I need more audio V than my Mp3 player or my android can supply ? Thanks in advance for any help
Registered Member #96
Joined: Thu Feb 09 2006, 05:37PM
Location: CI, Earth
Posts: 4061
IIRC the 555 needs to be biased between 1/3 and 2/3 Vcc to get any significant change in frequency and pulse width. So for an input voltage of 12V the signal would need to be centred at 8V and be 3V p-p in order to change the frequency by the needed amount.
Another method is to leave the frequency alone and change the average current in the arc which is done by altering the available input current with a series MOSFET in the power line. This approach is used on CCFL inverters on monitors, and results in a near 100% brightness control when the lamp current is part of the feedback loop.
IIRC the 555 needs to be biased between 1/3 and 2/3 Vcc to get any significant change in frequency and pulse width. So for an input voltage of 12V the signal would need to be centred at 8V and be 3V p-p in order to change the frequency by the needed amount. Another method is to leave the frequency alone and change the average current in the arc which is done by altering the available input current with a series MOSFET in the power line. This approach is used on CCFL inverters on monitors, and results in a near 100% brightness control when the lamp current is part of the feedback loop.
-A
Could you explain this in a bit more detail? Sounds interesting
Registered Member #3637
Joined: Fri Jan 21 2011, 11:07PM
Location: Buffalo, NY
Posts: 1068
Tightmopedman9 wrote ...
Conundrum wrote ...
IIRC the 555 needs to be biased between 1/3 and 2/3 Vcc to get any significant change in frequency and pulse width. So for an input voltage of 12V the signal would need to be centred at 8V and be 3V p-p in order to change the frequency by the needed amount. Another method is to leave the frequency alone and change the average current in the arc which is done by altering the available input current with a series MOSFET in the power line. This approach is used on CCFL inverters on monitors, and results in a near 100% brightness control when the lamp current is part of the feedback loop.
-A
Could you explain this in a bit more detail? Sounds interesting
Sounds sorta like an SCR dimmer circuit with modulation...
Registered Member #579
Joined: Mon Mar 12 2007, 09:45AM
Location: Burntwood, Staffs, England
Posts: 46
thanks for the replies - especially conundrum Whoopee I now have got one working for more that a few minutes I have made some circuit changes - neon across the primary coil and some extra diodes . I will post circuit and video soon for others The Audio input was increased - as conundrum suggested ........... I got a alarm radio from ASDA ( USA = walmart) for £2 ( approx 3 USD.) mains operated , and wired in an audio out socket as there was not one built in It works well at the moment I will try some other circuits later but for now I can show it at the talk I am giving to-morrow Thanks all
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How to get a singing arc to work - from a fly back - help needed
