OT: fan control in MFJ-4225MV switching P/S
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OT: fan control in MFJ-4225MV switching P/S
 
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This could almost be "on topic", as the desire to control the fan in my
MFJ-4225MV P/S is associated with my acquisition of a K3. There was recently a discussion of switching power supplies for the K3 on the list. I thought the MFJ unit was quiet while others found it to be noisy. After the noisy fans in my FT-1000 and in my old PC left the shack, the MFJ P/S did become the loudest box in the vicinity. I had a sense that the P/S didn't really need that continuous fan activity, especially during low duty cycle operation or just listening. So I put a temperature sensor on a heat sink and use it to turn the fan on and off via a comparator circuit and MOSFET switch. I think it's going to work out pretty well. Of course, the simple circuit could be used on any P/S that runs the fan all the time but doesn't really need to. Schematic and lots of rambling chatter about the little project are here -- http://pages.suddenlink.net/wa5bdu/fan_control_page.html 73-- Nick, WA5BDU in Arkansas #1195 _______________________________________________ Elecraft mailing list Post to: [hidden email] You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com |
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As I'm not a very technical person I just used a couple of resistors in parallel to slow the fan down in my 4225. I can't remember the values this early in the morning but it seems to be working just fine. The supply does run a little warmer but not hot and the fan is no longer heard.
Bill NZ0T
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Re: OT: fan control in MFJ-4225MV switching P/S
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That's a pretty good solution. When I was making measurements I noted
that when I turned the supply voltage down to the 10 to 11 volt range the fan got very quiet. In fact, I was going to forget about the thermostatic control solution. But when I put the cover on, the noise worsened quite a bit at the same voltage. Pulling air through those case perforations seems to do it. Since the K3 is spec'd for 11 to 15 volts, I wanted to run at a little over 14 V or so. The fan really gets noisier as voltage climbs, so I definitely needed either the resistor solution or fan control. 73- Nick, WA5BDU NZ0T wrote: > As I'm not a very technical person I just used a couple of resistors in > parallel to slow the fan down in my 4225. I can't remember the values this > early in the morning but it seems to be working just fine. The supply does > run a little warmer but not hot and the fan is no longer heard. > > Bill NZ0T > > _______________________________________________ Elecraft mailing list Post to: [hidden email] You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com |
Re: OT: fan control in MFJ-4225MV switching P/S
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The cool (pun intended) way to do it is to use a thermostat wired in
parallel with a resistor in series with the fan. The fan only runs at full voltage when the heat sink gets hot. Another way is to use a thermistor and amplifier to gradually turn up the fan voltage as things warm up. The main concern is to be sure that the fan still turns on reliably with the resistor in series. I would test to find the largest resistance that allows the fan to start and use no more than half that value, to allow for changes in fan characteristics as it ages. Al N1AL On Mon, 2008-08-04 at 16:43, Nick-WA5BDU wrote: > That's a pretty good solution. When I was making measurements I noted > that when I turned the supply voltage down to the 10 to 11 volt range > the fan got very quiet. In fact, I was going to forget about the > thermostatic control solution. But when I put the cover on, the noise > worsened quite a bit at the same voltage. Pulling air through those > case perforations seems to do it. > > Since the K3 is spec'd for 11 to 15 volts, I wanted to run at a little > over 14 V or so. The fan really gets noisier as voltage climbs, so I > definitely needed either the resistor solution or fan control. > > 73- > > Nick, WA5BDU > > > NZ0T wrote: > > As I'm not a very technical person I just used a couple of resistors in > > parallel to slow the fan down in my 4225. I can't remember the values this > > early in the morning but it seems to be working just fine. The supply does > > run a little warmer but not hot and the fan is no longer heard. > > > > Bill NZ0T > > > > > > _______________________________________________ > Elecraft mailing list > Post to: [hidden email] > You must be a subscriber to post to the list. > Subscriber Info (Addr. Change, sub, unsub etc.): > http://mailman.qth.net/mailman/listinfo/elecraft > > Help: http://mailman.qth.net/subscribers.htm > Elecraft web page: http://www.elecraft.com _______________________________________________ Elecraft mailing list Post to: [hidden email] You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com |
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Alan Bloom wrote:
>The cool (pun intended) way to do it is to use a thermostat wired in >parallel with a resistor in series with the fan. The fan only runs at >full voltage when the heat sink gets hot. > The Astron SS-30 has a very noisy fan that is controlled by a thermal switch on the heatsink. But there isn't sufficient cooling when the fan is off, so every few minutes brings another blast of fan noise. A 100-ohm 3W resistor in parallel with the thermal switch will keep the fan running slowly and quietly, all the time. With a typical load from a "100W" transceiver, I've never heard it switch to full speed again. >The main concern is to be sure that the fan still turns on reliably >with the resistor in series. I would test to find the largest >resistance that allows the fan to start and use no more than half that >value, to allow for changes in fan characteristics as it ages. Agreed. 100 ohms gives brisk and reliable starting for that particular 12V fan, but other fans will vary. -- 73 from Ian GM3SEK 'In Practice' columnist for RadCom (RSGB) http://www.ifwtech.co.uk/g3sek _______________________________________________ Elecraft mailing list Post to: [hidden email] You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com |
Re: OT: fan control in MFJ-4225MV switching P/S
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In reply to this post by Nick Kennedy
I used a 5 volt regulator on my MFJ 4225 to slow down the fan. This allows
the fan to start reliably at any voltage. I have run mine and my K2-100 this way for at least 5 years with no problem on SSB, CW and DIGITAL. 73 Ken W0CZ Bill NZ0T Wrote <As I'm not a very technical person I just used a couple of resistors in <parallel to slow the fan down in my 4225. I can't remember the values this <early in the morning but it seems to be working just fine. The supply does <run a little warmer but not hot and the fan is no longer heard. < <Bill NZ0T _______________________________________________ Elecraft mailing list Post to: [hidden email] You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com |
Re: OT: fan control in MFJ-4225MV switching P/S
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Yes, I expect a voltage regulator would work better than a resistor to
drop the voltage. Since the fan motor draws more current at startup than when it is running, a contant-voltage source should give more-reliable startup at a lower voltage. But you probably still want to use a thermostat or some other method to switch the fan to full voltage if things get too hot. Al N1AL On Tue, 2008-08-05 at 05:06, Kenneth A. Christiansen wrote: > I used a 5 volt regulator on my MFJ 4225 to slow down the fan. This allows > the fan to start reliably at any voltage. I have run mine and my K2-100 this > way for at least 5 years with no problem on SSB, CW and DIGITAL. > > 73 > Ken W0CZ > > Bill NZ0T Wrote > <As I'm not a very technical person I just used a couple of resistors in > <parallel to slow the fan down in my 4225. I can't remember the values this > <early in the morning but it seems to be working just fine. The supply does > <run a little warmer but not hot and the fan is no longer heard. > < > <Bill NZ0T > > _______________________________________________ > Elecraft mailing list > Post to: [hidden email] > You must be a subscriber to post to the list. > Subscriber Info (Addr. Change, sub, unsub etc.): > http://mailman.qth.net/mailman/listinfo/elecraft > > Help: http://mailman.qth.net/subscribers.htm > Elecraft web page: http://www.elecraft.com _______________________________________________ Elecraft mailing list Post to: [hidden email] You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com |
Re: OT: fan control in MFJ-4225MV switching P/S
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Just a thought here...
There are many fans for computers which have a thermal control for the fan speed built in. I suspect it's just a temperature-variable resistor in series with the power lead. This could be a viable alternative for cooling of almost any thing which needs it, and these things are cheap. Look for phrases like "thermally controlled", "temperature controlled" etc. With just a bit of searching, one can also find fans listed as "silent". Many sellers of these fans list the sound level in DB, which makes comparison easy, they almost always list RPM and CFM specs as well. Also a variety of sizes from 40mm to 120mm and more. Try Cooler Guys <http://www.coolerguys.com/>, NewEgg <http://www.newegg.com/>, Xoxide <http://www.xoxide.com/casefans.html?> just to name a few. Hope this may help. 73, John W4CWZ Alan Bloom wrote: > Yes, I expect a voltage regulator would work better than a resistor to > drop the voltage. Since the fan motor draws more current at startup > than when it is running, a contant-voltage source should give > more-reliable startup at a lower voltage. > > But you probably still want to use a thermostat or some other method to > switch the fan to full voltage if things get too hot. > > Al N1AL > > > On Tue, 2008-08-05 at 05:06, Kenneth A. Christiansen wrote: > >> I used a 5 volt regulator on my MFJ 4225 to slow down the fan. This allows >> the fan to start reliably at any voltage. I have run mine and my K2-100 this >> way for at least 5 years with no problem on SSB, CW and DIGITAL. >> >> 73 >> Ken W0CZ >> >> Bill NZ0T Wrote >> <As I'm not a very technical person I just used a couple of resistors in >> <parallel to slow the fan down in my 4225. I can't remember the values this >> <early in the morning but it seems to be working just fine. The supply does >> <run a little warmer but not hot and the fan is no longer heard. >> < >> <Bill NZ0T >> >> _______________________________________________ >> Elecraft mailing list >> Post to: [hidden email] >> You must be a subscriber to post to the list. >> Subscriber Info (Addr. Change, sub, unsub etc.): >> http://mailman.qth.net/mailman/listinfo/elecraft >> >> Help: http://mailman.qth.net/subscribers.htm >> Elecraft web page: http://www.elecraft.com >> > > _______________________________________________ > Elecraft mailing list > Post to: [hidden email] > You must be a subscriber to post to the list. > Subscriber Info (Addr. Change, sub, unsub etc.): > http://mailman.qth.net/mailman/listinfo/elecraft > > Help: http://mailman.qth.net/subscribers.htm > Elecraft web page: http://www.elecraft.com > > -- "The real proof that there is intelligent life in outer space is that they haven't come here." _______________________________________________ Elecraft mailing list Post to: [hidden email] You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com |
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