driving electric motors

[axegrinder]

Hi guys
i am successfully driving electric motors with the PWM output from a 18x and 28x chips.
I drive a FET which drives the motor. low powered motors work fine but as the motors get more powerful they tend to make the micro cut out or do weird stuff. any ideas or will i have to post the circuit.

thanks for your input.

Malcolm

 

[MartinM57]

...or will i have to post the circuit

...yep

Otherwise people will wax lyrically for hours about power supplies, back EMF, protection diodes etc etc, whereas a quick squizz at the schematic will probably lead to the solution pretty quickly

 

[Dippy]

Absolutely.
For this sort of thing ALWAYS post schematics. Our powers of clarvoyancy have wilted.

Also: include description of motors and your PSU. Include component values.

If you want some techno answers the include LINKS to device data sheets.

The information YOU provide then the better/quicker the replies.

 

[BeanieBots]

With high power / currents, layout can be just as important as the components, so a picture would be just as useful as the circuit.

 

[manuka]

In case you didn't get the essence of the above - send circuit,layout picture, & links. Pondering this is often thirsty work,so we've no objection to also receiving folding stuff that suits local liquefaction. Stan.

 

[Wrenow]

Do keep in mind that more powerful motors can have huge increases in current draw under load. A common Mabuchi 550, for instance, can draw over 85A at stall (and momentarily at startup). This is 20 times the stall draw of the next smaller common hobby motor, the 380, aka the "Speed 400". And 80-100 times the stall draw of the 500TB (aka the Tamiya Solar Motor 01).

So, point being you can get some really serious power grains with more powerful motors, making best engineering practices more mandatory. Things you can get by with using smaller motors will not fly with higher draw beasts.

Hence, the repeated requests for diagrams, pictures, etc. When you are trying to protect a circuit from a 60-80A surge draw, 'tain't trivial. I have seen a pair of 550s literally melt the solder out of a USD$50 ESC on one ship in our Model Warship Combat club. The captain has since moved to a pair of 380s and is much happier (more reserve power in the batteries and, being geared to a better speed, better performance on top of that).

More power is not always the best solution. Sometimes leverage (in the form of gears and pulleys) is better. More power means heavier wiring, higher spec components, more battery capacity, etc. Costs tend to go up more exponentially than arithmetically.

Cheers,

Wreno