Why concentrate on stability for a junk circuit? Well this can run really and I mean really slowly so little drift as possible seemed like a good idea.Ĭould it be better? Yes, definately. ![]() The timing capacitors on the 555 are a tantulum, (1uF), and myler, (0.22uF), types to further aid stability. ![]() The ULN2003 is hooked up in such a way as to provide dual coil drive for a unipolar stepper motor so that it gains more torque to drive the 'dolly'.Ī 7805 regulator to provide 5 volts for the 555 timer and flip flop, (the stability of the 555 timer is much improved by doing this!), and the 12 volt from the battery pack driving the stepper motor. The 4013 provides a 00 count required for the boot-strapped ULN2003, a DPDT switch providing forward and backward drive, (by simpling reversing the connections). (ULN2003's might be hard to find off the parts shelf nowadays, this one was stripped from an old printer board but a ULN2803 or similar will do a nice job). ![]() The ubiquitous 555 timer, (hooked up for variable mark/space ratio, if you build one you'll find out why it's needed), and a couple of D type flip-flops, (4013), to provide the count for the ULN2003 stepper motor driver. Here's the circuitry for the stepper motor driver for my DIY camera dolly.
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June 2023
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