Electronic project help

[abunaitoo]

So many smart people here, I'm hoping someone would know about these things.
So, I'm trying to replace the motor, on my band saw, with a variable speed DC motor.
I have it working, except I need a lower ohm potentiometer, that I need to order.
I want to put a fan over the speed control.
I have some computer fans that look like they will work.
What I'm looking for is someway to keep the fan running, for about a minute, after the motor is turned off.
Has to be something cheap and small.

[popper]

A switch?
Any contact type kind of timer would work but extra $.

[Mal Paso]

12 Volt DC? This may work. https://www.littelfuse.com/products/protection-relays-and-controls/time-delay-relays/delay-on-break/krdb.aspx They have 120 Volt too. It's called a delay on break relay. https://www.littelfuse.com/products/protection-relays-and-controls/time-delay-relays/delay-on-break.aspx

[Frosty Boolit]

A delay on break relay can be found in an old furnace for the blower fan.

[jsizemore]

Might be kinda hard to find a household furnace in Hawaii.

[Frosty Boolit]

I'd imagine they have heat pumps which should have the same type of relay

[BamaNapper]

Amazon has an assortment of time delay relays that would probably work well for you. Without knowing voltages it's hard to point to one in particular. The one I opened up first was part number B07BT25J52 which says the delay is adjustable up to an hour.

Did you consider using a 'buck converter' for the speed control. You mentioned using a pot to vary the speed so I assumed you're limiting the current to the motor with the pot/rheostat. A buck converter would provide a variable DC voltage source, and they're pretty efficient so don't produce much heat. Also they're pretty cheap and easy to hook up. Varying the voltage instead of the current could make for a better speed control since the motor would be able to draw more current at the same voltage for more power as you ran something through the saw. Again, with no details I took a quick look at higher power buck converters. Perhaps Amazon pt B081X5YX8V? It would be a simple matter to solder on an external pot and knob in place of the little pot mounted on the card.

[abunaitoo]

Should have posted more information.
It's a project I'm trying.
Old treadmill brush motor.
AC speed control from amazon, going through a bridge rectifier.
It seems to be working.
The pot needs to be changed because it's to high.
need to turn it almost 3/4 to start the motor.
I'm going to add a fan to keep things cool, and want the fan to keep on working after the motor stops.
But don't want it running all the time, and don't want to use a switch to turn it on and off.
Getting old and I know I'll forget to turn it off.
So I'm thinking something 110vac.
I found an old small 110vac fan out of an icebox that looks like it would work.
Kind of an interesting project.

[farmbif]

what brand speed controller, some have optional heat sink that are very effective

[abunaitoo]

I got it from amazon.
Cheap chinese junk, but it's working for now.
DIANQI 4000W Motor Speed Controller, Motor Control Board AC 10-110V Adjustable Voltage Regulator SCR High Power Dimmer Controller Temperature Governor Dimming Monitor
There is a heat sink in it, but none on the bridge rectifier.

[10x]

If heat on the speed controller is an issue a heat sink combined with a fan will likely keep it alive longer.
On the other hand if you have the correct high amp potentiometer you may not need more than passive cooling.
If you have to cool the potentiometer, it may not have the capacity to run the motor and will fail.


https://www.google.com/search?q=high+amp+potentiometer&oq=High+amp+pot&aqs=chrome.1.69i57j0i22i30j0i390l3.8407j0j7&sourceid=chrome&ie=UTF-8

[abunaitoo]

I'm just going by what was posted on utube.
After all everything on the internet is the truth.....right.
Haven't tried to run it very long.
Probably should do that first.
Motor get warm, but I'm guessing that's normal.

[jsizemore]

I'd imagine they have heat pumps which should have the same type of relay

If it gets cold over there, you got the AC set too low. It did get chilly when I was in a walk-in cooler or freezer. When I left from over there I didn't own a jacket. My buddy picked me up at SEATAC and carried me to JC Penney's to get one.