Knowlege is power Posted July 12, 2005 Report Share Posted July 12, 2005 I buit a driver for an ignition coil where the out put goes directly to the base of a 2n3055 transitor to triger the pulses through the coil and it dosent work.The spark is so pitiful that I'd fell safe putting the HV wire in my mouth (not recomended) The 2n3055 transistor is rated at 15A and the maximus curent draw from the ignition coil acording to ohms law is about 7.5A 1.6 ohms, 12v only half of what the 2n3055 can handel so it should not have blown, could this be because the pulse from the 555 is not powerful enough to make the transitor fully conductive, and using a transitor to amplify the pulse make it work. if anyone can help it would be much apreciated. also if i have a picture on my PC that a want to display in a post how do i go about it. Quote Link to comment Share on other sites More sharing options...
steven Posted July 12, 2005 Report Share Posted July 12, 2005 hello knowledge is power , that has allways been my beleaf that knowledge is power. look at my ignition coil driver circuits posted in the high voltage stuff section and you can even power 2 ignition coils in parralell to , or if you want big arcs use a high voltage trippler with your single ignition coil , youll see pictures of my ignition coil drivers i biult from circuits ive collected and the modifications ive made to them , and the high voltage dc output tripplers i used Quote Link to comment Share on other sites More sharing options...
ante Posted July 12, 2005 Report Share Posted July 12, 2005 Hi Knowlege,One way to know if the transistor is doing a good switching job is if the transistor is cool. With a 2N3055 in and optimal circuit chopping 7.5A will only be slightly warm. The 555 can supply 200mA so a beta of at least 40 is necessary and the 2N3055 does not have a beta of 40, it’s only about 20 at 4A. Can you post the circuit? Quote Link to comment Share on other sites More sharing options...
audioguru Posted July 12, 2005 Report Share Posted July 12, 2005 Hi Ante,A typical 2N3055 has a beta of 35 at a collector current of 4A and a Vce of 4V. Its minimum but still guaranteed beta is only 20.Its saturation region is another story. It ain't going to saturate without a whopping high base current. ;D Quote Link to comment Share on other sites More sharing options...
ante Posted July 12, 2005 Report Share Posted July 12, 2005 Well, that’s about what I said! ;D ;D Quote Link to comment Share on other sites More sharing options...
steven Posted July 13, 2005 Report Share Posted July 13, 2005 the fine details hey, has anyone gone into the molecular structure of the transistor yet ha ha ha ha and back to roswell where it was rumoured it orinated from as a product of reverse engineering of crashed alien space craft ha ha ha ha Quote Link to comment Share on other sites More sharing options...
steelsiv Posted July 14, 2005 Report Share Posted July 14, 2005 What everyone is saying is that a 555 does not put out enough current to drive the power transistor into saturation (all the way on). Quote Link to comment Share on other sites More sharing options...
Knowlege is power Posted July 14, 2005 Author Report Share Posted July 14, 2005 Thanks for the help, so using the transistor mentioned or something similar, with the 555 pulse to the base and the emmiter to the base of the power transistor, or would i need a slightly more complex cicuit. If someone tells me how to post a picture that i have on my PC, i will post a schematic of the circuit that i am going to use. also i have read that the NE555 is only good up to 50KHz is this true. thankyou. Quote Link to comment Share on other sites More sharing options...
audioguru Posted July 14, 2005 Report Share Posted July 14, 2005 so using the transistor mentioned or something similar, with the 555 pulse to the base and the emitter to the base of the power transistor, or would i need a slightly more complex circuit?The collector of the added transistor should be connected to the positive supply. If you don't use a resistor in series with its base to limit the current then its base will probably blow-up. If someone tells me how to post a picture that i have on my PC, i will post a schematic of the circuit that i am going to use.Additional Options, Browse, select and click "open" the circuit's file on your hard drive then Post.I have read that the NE555 is only good up to 50KHz, is this true?Don't you have its datasheet? Quote Link to comment Share on other sites More sharing options...
Knowlege is power Posted July 14, 2005 Author Report Share Posted July 14, 2005 Thanks This is the Circuit I plan to use partly my design and partly not. Diode pot configuration alows for independant control over the high and low pulse duration and R2 ajust the over all frequency. havent decided on the best valuse yet. Quote Link to comment Share on other sites More sharing options...
audioguru Posted July 14, 2005 Report Share Posted July 14, 2005 Your circuit doesn't need R5. R6 limits the current of TR1 and the base current of TR2.TR2 needs a resistor to ground at its base to turn it off quickly. ;D Quote Link to comment Share on other sites More sharing options...
steelsiv Posted July 15, 2005 Report Share Posted July 15, 2005 audioguru is right. The biggest problem working with high voltage and/or high current is zapping you transistor. It's not hard to build up spikes that will kill your transistor. A diode in reverse polarity across the coil is a good place to start. If your transistor gets zapped, a snubber circuit may be needed. Working with high voltage/high current can be a very hit and miss project. Have fun. Quote Link to comment Share on other sites More sharing options...
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