stepper motor problems

[mikeb]

im here again with a whole new problem? im trying to interface a ede1200 stepper motor ic to a 5 v 7.5*step angle 1.38 amp unipolar stepper motor. the data sheet for the ic has a hookup diagram for motor that drawup to 10 ampsper phase. the circuit is basically 4 mje3055 power transistors used as switchs with a diode acroos the collector lead to +5volts that amplifys the input current to a value large enough to drive each phase of the coil. i have connected the motor for test by connecting both common leads to +5 volts and touching each successive phase lead to gnd and the motor works well. i placed a meter in series with each lead for each coil i was testing and it shows that each phase is drawing approx 1 amp when connected to gnd. when i connect the driver ic each phase is only drawing 139 milli amps and the motor doesnt turn it seems to shimmer a bit as if it wants to turn so i checked that the pahse wires were correct and they are so i figured that the driver is not producing enough drive current to drive the collector which drives each coil. my question is how can i increase the collect current up to 1 amp to drive each phase.
the base resistor is 2k.

[Edd]

Since you’re already committed on the parts on hand, how about the simplest initial procedure of making those 3055’s into darlingtons by putting an npn 2N2222 [Or the equivalent that you might have in stock] on each of their front ends to enact a higher beta/sensitivity. Connect Common collectors and the 2222’s emitter couples into the 3055’s base with the IC’s stepper drive feeding into the 22222’s base.With your test of one coils potential power drain, this should saturate and only having the loss of the 3055’s junction.<p>73's de Edd
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[mikeb]

edd are you saying connect a darlington to each 3055 input at the base by making the 3055 a darlington with the first input transistor being a 2n2222a, with its collector connected to the collector of the 3055, and the emitter of the 2n2222a connected to the base of the 3055, which would create the darlington with the input transistor being a 2n2222a or am i missing the point.

[Edd]

Righto... make each 3055 into a darlington with an NPN 2222....or what have you ........ equivalent ...as its front input transistor. Wired exactly as you had interpreted it in your last statement.At specific times I have even placed another 2222 at the input of the first 2222 making a triple darlington .
73's de Edd