Hi All!
I recently decided to build one of these units to replace the stock fixed ingition on my son's go kart.
I currently have two units running, one test setup built on a breadboard and the other as a "production unit." I have used an off the shelf toroidal
http://www.jaycar.com.au/productView...p;form=KEYWORD
for the DC-DC upconvertor to charge the capacitor. I initially had trouble with controling the voltage on the main cap.
At first, I could get only about 180 V max. I changed C7 to .2uF and R5 to 300Ohms. This made the charger go into "overdrive." At one point I had over 1000 volts on it before the BT151 gated itself! I found that I could control this by having a ~1M pot pulling down the voltage to 400V while idle (no spark). In test function 1 (300 rpm) , the voltage drops to ~370V. In test function 2 (7500 rpm), it drops to 30V.
I am using this setup:
http://www.modelbouw.gompy.net/newcdi/cdi-a.jpg
I noticed that Bigboat had similar trouble some time ago:
I have test today the CDI and find some problems.
Sometimes I missing a spark, sometimes a spark at the wrong time or to muts sparks at the same time.
It seems to me a EMC-problem in the pcb I use, the pic making (or not) his own sparks.
Also the energy for the capacitor is to small when the engine runs high rpm.
If I calculate the power I need (5 Watt), the capacitor must be ~4,7uF instead of 1uF.
Inside the cylinder the pressure is ~12bar on 4000
<font color="#000000">rpm</font>, with this pressure there isn't a spark anymore.
Back to the drawingbord [img]{akamaiimageforum}/image/s14.gif[/img]
Does the 1N4007 need to be inverted or has this already been udated in the schematic?
Any other suggestion to keep the charge on the main cap up to working level?
R's
JP
p.s apologies in advance if I missed the answer already posted.....I did read thru all 12 pages & didn't find it.