crazybuoy Posted September 29, 2010 Report Share Posted September 29, 2010 I am going to build following circuit to run stepper motor using TIP142. So is there any need to change any thing in this circuit? The schematic of circuit is attached with this post. Quote Link to comment Share on other sites More sharing options...
audioguru Posted September 29, 2010 Report Share Posted September 29, 2010 When any of your darlington transistors turns on, it is a dead short from the +24V supply to ground. The coils in your motor are never powered because both of their wires are always at +24V.All outputs of your darlington transistors are shorted together. Quote Link to comment Share on other sites More sharing options...
Hero999 Posted September 29, 2010 Report Share Posted September 29, 2010 The only thing which should be connected to +V is the stepper motor common wire.You should consider using logic level MOSFETs rather than Darlington pairs because they turn off faster and have lower losses. Quote Link to comment Share on other sites More sharing options...
crazybuoy Posted September 29, 2010 Author Report Share Posted September 29, 2010 Thanks, how about the value of resistor? Quote Link to comment Share on other sites More sharing options...
Hero999 Posted September 29, 2010 Report Share Posted September 29, 2010 That depends on the logic voltage and collector current.With 2k2 and a logic voltage of 5V:IB = (V-VBE)/RB = (5-1.4)/2200 = 1.6mASo you'll be restricted to a couple of amps before the saturation voltage becomes unacceptable.. Quote Link to comment Share on other sites More sharing options...
crazybuoy Posted October 3, 2010 Author Report Share Posted October 3, 2010 Now, I have try this circuit with 24V DC, 1.7Amp power supply. But still the motor does take any step (forward or backward). I think the value of resister is very much big. What it should be? And I could not understand your formula. Now how can I use it with above power supply? Quote Link to comment Share on other sites More sharing options...
Hero999 Posted October 3, 2010 Report Share Posted October 3, 2010 IB = base current.V = logic voltage, which you haven't given so I assumed 5V.VBE = base emitter voltage which is on the datasheet and is typically 1.4V for a Darlington pair.The TIP142's saturation voltage (VCEis specified with IB = IC/100.With an IC of 1.7A and an IB of 17mA, VCE is typically 0.75VIf the base current is lower, then VCE will be higher, if IC is still 1.7A but IB is reduced to IC/4000 = 425 Quote Link to comment Share on other sites More sharing options...
crazybuoy Posted October 15, 2010 Author Report Share Posted October 15, 2010 Thanks guys, I have try to install 1K variable resistor and have adjust it to many values. But still the motor does not move any step. Is there any way to troubleshoot the circuit? Quote Link to comment Share on other sites More sharing options...
Hero999 Posted October 15, 2010 Report Share Posted October 15, 2010 There's no need for a variable resistor. You could have destroyed the controller output by setting it to too lower value. Use 220R, as I said in my previous post.I would help you to troubleshoot the circuit if you post the whole circuit rather than just part of it. Quote Link to comment Share on other sites More sharing options...
crazybuoy Posted October 16, 2010 Author Report Share Posted October 16, 2010 There is complete circuit in this[//url] thread. I have post all info about it. Ok now I will try fixed resistor. I am only wonder why the transistor not switched on to run the motor. Quote Link to comment Share on other sites More sharing options...
Hero999 Posted October 16, 2010 Report Share Posted October 16, 2010 That's not the complete circuit, it doesn't show what's driving the transistors. Quote Link to comment Share on other sites More sharing options...
crazybuoy Posted November 3, 2010 Author Report Share Posted November 3, 2010 Now following stepper driver is successful to run the steps of motor. But there is a problem that the transistors turn hot very quickly. What is problem here. I think the resistor is small. Is it? Quote Link to comment Share on other sites More sharing options...
Hero999 Posted November 4, 2010 Report Share Posted November 4, 2010 If you want help, post the complete circuit, including what is driving the transistors. Quote Link to comment Share on other sites More sharing options...
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