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RE: Rheostat
To: "crtech@crtech.org" <crtech@crtech.org>
Subject: RE: Rheostat
From: Mike Price <mprice@srnradio.com>
Date: Wed, 18 Apr 2018 14:51:58 +0000
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Thread-topic: [CRTech] Rheostat
How about a poor man's voltage regulator?  A 1K ohm pot and a NPN power transistor like a 2n3055.  The collector and one end of the pot goes to the positive supply voltage.  The wiper of the pot goes to the base. The emitter goes to the fan. The other end of the pot goes to negative common.  Depending on how much the fan draws, the transistor may need a heat sink.

Cheers,

Mike Price



-----Original Message-----
From: Terry Cowan [mailto:tcowan@knlr.com] 
Sent: Tuesday, April 17, 2018 11:43 AM
To: crtech@crtech.org
Subject: Re: [CRTech] Rheostat

Several (or more) diodes in series will drop the voltage which should 
slow the fan speed.
Terry Cowan
KNLR/KNLX

On 04/17/18 09:21, Tim Roberts wrote:
> The fan in our STL transmitter went out a couple years back. When we 
> received the replacement fan ($182) we discovered that whatever 
> controls the fan speed had gone out as well and to fix it we'd have to 
> send it back to the manufacturer. Rather than deal with that I pulled 
> the new fan as a backup for our STL receiver and we put an $18 fan I 
> found on DigiKey in it( 
> https://www.digikey.com/products/en?keywords=603-1523-ND ). Since that 
> time I've tried to get the guy that helps us with engineering to put 
> some type of control on it such as a rheostat to keep it from running 
> full blast constantly. Needless to say it's been low on his priority 
> list and the fan finally burned out last night. Could someone give me 
> a bit of direction in what I need to get to control this thing? Our 
> engineer guy said quite a while back he had found something for about 
> $20 that would do the trick, but he never gave me the info to order 
> it. Right now he's in Tennesee for a few days. I appreciate any and 
> all help on this. We can get it taken care of without him, but just 
> need help on what exactly we need...
>
> Thanks,
> Tim Roberts
> Operations Director
> 89.5 KMOC Texoma

References: Re: Rheostat
(Terry Cowan <tcowan@knlr.com>, 17 Apr 2018 16:43:35 -0000)
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