I have a 135mm diameter turntable for models. powered by the 28BYJ-48 stepper motor using a 5v transformer. I have set the unit to rotate clockwise at 2rpm with full 360 degree rotation.
However after turning it off and then back on It does not restart. If I press a button it then restarts at clockwise 2rpm full 360 rotation. Is it possible to make the unit restart when the power is turned back on? It is a Chinese unit and has three buttons with a circuit board which I do not understand! I am hoping it is just a matter of soldering in a jumper wire to make it restart when powered on. Due to the unit being in a display cabinet it is not feasible to press a button every time. I hope someone can help me!!!
c_mitra.
Thanks very much for your help. have attached three pics which I hope will make sense to you.
I am much more of a mechanical guy than a electronics guy!
The motor appears to have internal gears (because the drive spindle is offset from the axis). The speed reduction increases the torque and a small motor can be sufficient. I cannot make out the labels on the ICs but they are related to drive circuit.
One of them is a driver and the other may be the real controller. I could not make out much.
In the worst case, you can solder two wires from the switch and bring them out to any convenient position. As these are low frequency devices, you are unlikely to have any problem.
One of the ICs on the pcb is ULN2003. The other one is, probably, microcontroller.
As for the motor, it is unipolar motor, 5 wires, common wire connected to positive supply, phase wires connected through ULN to ground sequenced by microcontroller.
c_mitra and ZASto, thanks very much for your info.
c_mitra--I have soldered two wires to the switch and it works fine. I will purchase a switch and fit it to the outside of the cabinet.
A brilliant solution, it is great to know that there are experts who are willing to pass on their knowledge free of any charge to an unknown person.