Hi Josh,
	I would like to recommend you to take a look at the IPS (Intelligent
Power Switch) that IR was to offer. It is under the automotive section on
www.irf.com

	An IPS is basically a MOSFET with a driver and some protection
features like short circuit, battery reversal protection and over current
among others. You can even measure the current consumption and detect open
load (load removed).

	There is a big spectrum of solutions, but I think that you need
something that can support 24V (the 70V devices are for 24 inductive loads,
since your load is resistive, you can use the 40V devices). The device
should also be able to handle 11A or more and support a switching frequency
of, at least, 100 Hz to make sure the PWM is not seen.

	There are high and low side drivers.

	I have chosed one for you, the IPS6021SPBF
(https://ec.irf.com/v6/en/US/adirect/ir?cmd=3DcatSearchFrame&domSendTo=3Dby=
ID&do
mProductQueryName=3DIPS6021SPBF). This device can withstand up to 12A
continuous output at 85=B0C on the TO220 model with a heat sink. The intern=
al
current limit is set to 32A.

Regards,

> -----Original Message-----
> From: piclist-bounces@mit.edu [mailto:piclist-bounces@mit.edu] On
> Behalf Of Josh Koffman
> Sent: Wednesday, November 04, 2009 21:55
> To: Microcontroller discussion list - Public.
> Subject: [EE] 24V Dimmer
> =

> Hi all. I might be called on to help out with a project. The part I'm
> most unsure about is that the intensity of a 24V 250W light bulb will
> need to be controlled, preferably by a PIC. It's being supplied by a
> 24V battery.
> =

>  I'd love to be able to find a compact, ready made module that would
> do this part for me. Digital (ie serial data, etc) control would be
> ideal, but analog might be possible. Alternatively I could use the CCP
> module to generate some PWM, but I'd need a driver. The reason I'd
> like a module is that in the event of a problem it would be easy to
> swap out. I've done some searching and what I'm finding are a ton of
> smaller modules meant for dimming LEDs.
> =

> Alternatively I could use PWM and some sort of home built driver. The
> circuit here: http://www.solorb.com/elect/solarcirc/pwm1/ suggests the
> use of a FET. Having never controlled this large a DC load before, I
> have no idea if this is a good or bad idea. Any thoughts?
> =

> Thanks for the help!
> =

> Josh
> --
> A common mistake that people make when trying to design something
> completely foolproof is to underestimate the ingenuity of complete
> fools.
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> --
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