[dorkbotpdx-blabber] 12 volt 20 amp power supply to drive a couple of pumps

[Dem Chi]

Sadly, the motors are more complicated than that. They have built in
pressure sensing so that they turn on when the pressure in their lines drops
below 100psi. If they weren't, then I would just control them that way.

So basically this is how things are set up: We have a pump drawing rainwater
from a rain barrel and pushing it into an RO system and then into a clean
water storage tank. There are float switches in both rain barrel and the
storage tank to tell things when to turn off and on. I control a solenoid
valve between the pump and the RO system to turn off the system (shut it and
the pressure quickly reaches 100psi and the motor shuts down). When we want
clean water from the barrel, we open another spigot and the pressure in that
line drops turning on the other pump which draws water from the clean
storage tank and pumps it out our spigot to do with what we like.

The solenoid valve runs on 24 volts at 0.4A. The two motors we know already
and the arduino which controls the logic.

I really like the idea of scavanging parts from cheap Harbor Freight stuff
that Eric suggested. Very nice.

On Sun, Mar 15, 2009 at 10:00 PM, Paul Stoffregen <paul at pjrc.com> wrote:

>
>  I'm getting a 24V line at
>> ~20 amps. I need to take this down to a 12 volt line and current limit it
>> so
>> that I don't burn up my pumps.
>>
>
> Maybe if you drive the motors with PWM right from the 24 volt line,
> averaging about 50%, you can avoid needing to regulate down to 12 volts?
>  Then all you need is a big MOSFET, probably rated for 40 volts or 50 volts,
> and a lot of current, and probably a special driver chip to drive its gate
> quickly.
>
> Of course, some sort of current sensing to control the PWM can also
> implement the current limiting, rather than needing expensive circuitry...
> maube?
>
>
> _______________________________________________
> dorkbotpdx-blabber mailing list
> dorkbotpdx-blabber at dorkbot.org
> http://music.columbia.edu/mailman/listinfo/dorkbotpdx-blabber
>



-- 
http://www.urbansurvivalists.com/
-------------- next part --------------
An HTML attachment was scrubbed...
URL: http://music.columbia.edu/pipermail/dorkbotpdx-blabber/attachments/20090315/a46d3714/attachment.html