ESP8266 Community Forum

- Mon Mar 12, 2018 4:02 pm #74557 Thanks for your time Rudy. I appreciate it.

The first thing I would do is to put a diode in series with the power supply. This should go a long way in protecting your circuit when someone connects the power backwards.

If I were to continue using the voltage regulator rather than a buck converter, (I would like to use a buck converter or switch mode power supply but fear the design of such is above my ability), then would inserting a schottky diode in series as you suggested and then inserting a Transil to ground like the following be ok do you think?

power supply.jpg

I designed a speed controller for electric motor on a salt and sand spreaders just over a year ago. One 3/4 hp motor on the conveyor and 1/3 hp on the spinner. It is for 12 volt battery systems and that meant the currents were pretty high. At the rated load the motor currents were 55 Amps and 27 Amps. Overload was higher than that. We used a variable current limit that allowed for short term overloads and motor start up. Protection of the CPU core wasn't too hard but the power section was a little more difficult (costly).

One of the reasons I am using a stepper motor in this project is because we tried a dc motor but gave up trying to get a wide enough operating rev range and still have enough torque to drive the equipment. I used an "off the shelf" 43a H-bridge driver for our testing.

Many thanks Rudy.

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- Mon Mar 12, 2018 4:40 pm #74559 You don't really need to design a buck converter. You can get little buck converter modules that will efficiently down convert; easier to use than a linear regulator.

Search ebay for mini buck converter.

- Mon Mar 12, 2018 5:34 pm #74560

If I were to continue using the voltage regulator rather than a buck converter, (I would like to use a buck converter or switch mode power supply but fear the design of such is above my ability), then would inserting a schottky diode in series as you suggested and then inserting a Transil to ground like the following be ok do you think?

power supply.jpg

The way you connected D4 it will short to ground, you need to switch it around. This device is basically a zener diode that can withstand high voltage surges, google for "zener diode" for an explanation how these work.

As buck converter I would recommend MP1584 based ones.
That chip is rated for up to 28V input, so it should be suitable for your application and you can get ready to use modules from aliexpress or ebay for about 2$/5pcs.

- Mon Mar 12, 2018 6:41 pm #74561

As buck converter I would recommend MP1584 based ones.
That chip is rated for up to 28V input, so it should be suitable for your application and you can get ready to use modules from aliexpress or ebay for about 2$/5pcs.

He said that it might be used on 24 volt vehicles. Even if it were only 12 volt vehicles a 28 volt maximum input capability is marginal. 60 volts is my target but 40 volts I grudgingly accept. (on 12 volt systems)

Schottky diodes are great but they have a lower reverse breakdown voltage. I use a general purpose silicon diode. A transorb/transil is great but you want to have some impedance between it and the electrical system. A "polyswitch" resettable fuse is worth looking at. You can't clamp the electrical system, you just need to prevent spikes and surges from getting into your electronics.

I also try and include a series inductor to keep high frequency transients out. Basically you want to pass nominal dc voltages and block what you can and then clamp what you couldn't block.

In one of my designs I included a higher voltage transistor in series with the circuit. Normally it is on and passes power to the voltage regulator. But if the voltage gets above 20 volts it turns off and keeps the regulator from seeing that surge.

You need to protect the stepper driver as well.