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DRSSTC8 with new driver and primary feedback (Brick fullbridge)

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LAN_403

Reaching

Wed Feb 13 2008, 08:22PM

Registered Member #76 Joined: Thu Feb 09 2006, 10:04AM
Location: Hemer, Germany
Posts: 458

finished the coil after hours of debugging. so as a good tip. never use a bipolar transistor for your overcurrent protection circuit. always use mosfets! .
had a horrible error and spent hours to get it. the bipolar transistor picked up noise and interruptet the interrupter signal. on the scope it looked like some harmonics in the primary circuit due to detuning etc. dont know. however, found the failure and now the coil works wunderful. made a few tests yesterday with 50% input voltage and hit the 1 meter target with only 90ÂµS of on time
no problems at all

heres a pic of the finished coil

and heres a link to youtube, showing the coil playing the starwars theme on half the input voltage

project is finished now :))))

Reaching

Sun Feb 17 2008, 09:00PM

Registered Member #76 Joined: Thu Feb 09 2006, 10:04AM
Location: Hemer, Germany
Posts: 458

made some pics with 75% input voltage (252V).. thats the max i can test in my room. the sparks are long enoough to hit the ceiling. to dangerous to go up to 310V max power. discharges are around 1.30meters long

Coronafix

Mon Feb 18 2008, 12:34AM

Registered Member #160 Joined: Mon Feb 13 2006, 02:07AM
Location: Melbourne, Australia
Posts: 938

Very impressive, Reaching!! How much power are you using to do that?
Is that half wave you are using?

Bennem

Mon Feb 18 2008, 05:38PM

Registered Member #154 Joined: Sun Feb 12 2006, 04:28PM
Location: Westmidlands, UK
Posts: 260

Great Sparks!.....Reaching
What peak primary current are you getting for that length of spark?

Mel.

Reaching

Mon Feb 18 2008, 05:57PM

Registered Member #76 Joined: Thu Feb 09 2006, 10:04AM
Location: Hemer, Germany
Posts: 458

For the pics i ran the coil at about 80 to 85% of max input voltage. Current draw was no more than 5A * 270V so around 1,3 to 1,4kW.
Peak primary current. Really i dont know. Due to the lack of time and my invitation to a german tv show on february 14th i fixed a failure the fast way and disabled the overcurrent protection circuit completely to get the the coil to work. so i really dont know, but i estimate the current to around 700-800A
sorry steve, but your overcurrent detection is not the way to go for me, worked exactly 0 times for me and brought more failures and bugs...

Bennem

Mon Feb 18 2008, 06:38PM

Registered Member #154 Joined: Sun Feb 12 2006, 04:28PM
Location: Westmidlands, UK
Posts: 260

Reaching wrote ...

sorry steve, but your overcurrent detection is not the way to go for me, worked exactly 0 times for me and brought more failures and bugs...

Its a shame that Steve's OCD circuit hasn't worked for you,
and looking at your site, you seem to have used his OCD in some of your
other coils with success.

Reaching

Mon Feb 18 2008, 07:44PM

Registered Member #76 Joined: Thu Feb 09 2006, 10:04AM
Location: Hemer, Germany
Posts: 458

with "success".. yeah if you call a red led flikkering success, then it is.
the cause iam a bit confused about this ocd stuff is, that i spend 2 days on the coil to find the bug. the circuit described by steve ward in his drsstc guide is the one i used in this drsstc without modifications. its the worst thing i ve done, cause i have some drsstc circuits which worked for me in the past.
the ocd simply wont work. i have exactly 3 fully assembled pcbs of steves driver and every pcb has the same bug in the ocd.
first of all: the ne555 in the ocd is wired wrong. the way which the trigger is wired, the 555 is completely nonsense, cause it cant do the job its used to. the pulselenght of the 555 is exactly the same lenght as the trigger is lower than 1/4 of input voltage.
Second: The mosfet stays on after an overcurrent detection.
third: the mosfet has no gate resistor, so the 555 can get destroyed due to overcurrent.
The overcurrent led wont light up,
etc etc
the rest of the circuit is fine, but the ocd is really crap, especially the way the high frequency waveform is rectified via 1n4148 without spending efford in calculating the voltage drop on the rectifier etc.
But, what am i doing here?
steves circuit workes for many people out there, and i wont be the first, who calls his work bad. there are just some simple things just as an ne555 wont work and a tlc555 "can" work. it depends on the parts. but i tried so many 555series, and especially with the ne555 and se555 i had many problems.
for those who are interested, i can make some pics of the board layout,..the pics are already uploadet to this forum and some checked the pcb for errors due to the same bug i had a year ago or so. the pcb has no errors

Bennem

Mon Feb 18 2008, 09:48PM

Registered Member #154 Joined: Sun Feb 12 2006, 04:28PM
Location: Westmidlands, UK
Posts: 260

Reaching wrote ...

finished the coil after hours of debugging. so as a good tip. never use a bipolar transistor for your overcurrent protection circuit. always use mosfets! .
had a horrible error and spent hours to get it.

Wasn't this an error of your own making and not of Steve's OCD circuit?
as he uses a mosfet and not a bipolar transistor in his circuit.

i spend 2 days on the coil to find the bug. the circuit described by steve ward in his drsstc guide is the one i used in this drsstc without modification

No modification??

Well.....i'm one of the many many folks who have had success with his circuit and
the only modifications needed to adapt to another persons coil is the
OCD burden resistor (depending on how much peak current you want to limit)
and RC timing network (depending upon the frequency of your coil)
but then again he explains this quite well in his write up.

Mel.

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