How to delay a power on and power off

capacitordelaypowerrelay

I need to delay power to the motors for my CNC driver project (using Toshiba TB6560 ICs, which require the motor power to be switched on after logic power and switched off before logic power).

I wanted to use a relay, which would be switched on by a RC delay circuit and enabled the motor power supply, and a big capacitor to supply the logic with power for a while after power off.

This is my current circuit:

enter image description here

Is this approach a good one? Would the circuit work?

Best Answer

I would use a timer (555) or small microcontroller (Attiny85) for sequencing the power. In fact, I do exactly this for one of my robots. Tie the source of the MOSFET to the gate of the MOSFET with a pull-up (4.7 kOhm is good) and tie a signal-level N-channel MOSFET like the BS170 to pull that gate down (thus turning on the P-channel) when given signal from the Attiny.

schematic

simulate this circuit – Schematic created using CircuitLab

You can use the ATtiny to sequence power however you want.

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