Electronics > Projects, Designs, and Technical Stuff
smps for dc motor
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Zero999:

--- Quote from: Benta on July 28, 2019, 05:12:13 pm ---Make it simple:
just measure the resistance of the motor (I assume it's a PMDC type), moving the armature until you have the lowest resistance. This will tell you the maximum current the motor is ever going to draw, at startup or under load.
Design accordingly.


--- End quote ---
Unfortunately that will end up in a grossly oversized the power supply.


--- Quote from: beanflying on July 28, 2019, 09:34:41 am ---What would 'measuring' a current that is going to smoke the brushes achieve?
--- End quote ---
What the heck are you on about? I said nothing about measuring a current which is going to smoke the brushes!

It's simple. Power the motor with the mechanical load connected, measure the current and size the switched mode power supply accordingly. Choose a power supply with plain old constant current limiting, not one which will shut down or fold-back and the inrush current will be a non-issue.
Benta:

--- Quote from: Zero999 on July 28, 2019, 10:13:04 pm ---
--- Quote from: Benta on July 28, 2019, 05:12:13 pm ---Make it simple:
just measure the resistance of the motor (I assume it's a PMDC type), moving the armature until you have the lowest resistance. This will tell you the maximum current the motor is ever going to draw, at startup or under load.
Design accordingly.


--- End quote ---
Unfortunately that will end up in a grossly oversized the power supply.


--- End quote ---

You completely missed the "Design accordingly" part. This was a hint to estimate the appropriate current limiting. I never suggested going to the max. but just to get a picture of the motor characteristics.

beanflying:

--- Quote from: Zero999 on July 28, 2019, 10:13:04 pm ---
--- Quote from: Benta on July 28, 2019, 05:12:13 pm ---Make it simple:
just measure the resistance of the motor (I assume it's a PMDC type), moving the armature until you have the lowest resistance. This will tell you the maximum current the motor is ever going to draw, at startup or under load.
Design accordingly.


--- End quote ---
Unfortunately that will end up in a grossly oversized the power supply.


--- Quote from: beanflying on July 28, 2019, 09:34:41 am ---What would 'measuring' a current that is going to smoke the brushes achieve?
--- End quote ---
What the heck are you on about? I said nothing about measuring a current which is going to smoke the brushes!

It's simple. Power the motor with the mechanical load connected, measure the current and size the switched mode power supply accordingly. Choose a power supply with plain old constant current limiting, not one which will shut down or fold-back and the inrush current will be a non-issue.

--- End quote ---



The OP stated initially he was going to use a Meanwell Power Supply and you ran off to reinvent the world with a current limited one he doesn't have. Operating current on some now additional information from the OP will most likely see currents lowish when running or he will be ripping the diamonds off the discs rather than grinding. I have had the issue with Chinese Power Supplies simply detecting a short circuit and not starting on larger motors if this is the case then additional current limiting or PWM would be a possible fix.

Meanwhile KISS this is a home use case not one that needs to be Engineered to death with imagined OTT solutions.
daniel444:
update
so i bought a HWS150A-24/A   ,  by TDK-Lambda
24v, 6.5a
it goes up to 28v
i got a good price for it on ebay, i think its new old stock

the motor resistance measures from 6 ohms to 30 ohms
these diamond discs are good for hand use as well
thanks for all the tips
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