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RE: [PSUBS-MAILIST] donation

Alan,
 
   In earlier testing (before I discovered the wonderful world of marine hailers) an attempt was made to use only the pcb board from similar 50 watt hand held bullhorns as the amplification for an underwater communications console.
   These were used in a similar manner as the lower transmit or "b" channel of DIY communications consoles in that this was "on" or active to transmit one's voice. When talking, it generated tons of heat that normally would have been dissipated.
   By hot I mean really hot! When used as originally intended, only when one pushed the talk button did power get applied to this card and it was allowed it to cool between transmissions. It was not designed to operate so confined in a small enclosure.
   I could have pursued this farther but hailers were found to do this job better and at a reduced cost.
 
                                                                                                                           David Bartsch
                                                                                      
From: alanjames@xtra.co.nz
To: personal_submersibles@psubs.org
Subject: Re: [PSUBS-MAILIST] donation
Date: Sat, 10 Jul 2010 13:10:10 +1200

Hi David,
Was it one particular component overheating in the bull horns?
Could it not have had a heat sink on it that maybe extended into the water?
I've been looking into the heating issue a little bit, with referance to my
pulse width modulators. They have a couple of Mosfetts that get quite hot.
I saw one PWM (on a truck) wich was only 12 volt 30 amps & had heat sinks
that extended out of its casing & a fan to cool the heat sink. However I
Googled & couldn't find any referance to them being a fire hazard.
Alan
----- Original Message -----
Sent: Saturday, July 10, 2010 12:33 PM
Subject: [PSUBS-MAILIST] donation

   Earlier this past Spring while researching underwater camera systems and periscope optics, I purchased a simple underwater camera with self contained lighting. This system could be lowered down to up to 60' and with the accompanying monitor brighten and clearly reveal anything within a few feet of this camera even if the water is very cloudy.
   Having found this particular system not to meet my present requirements and realizing the local rescue squad could really make use of this simple and portable tool to locate drowning victims, I donated it to them.
   Tomorrow my two boys and I get a picture taken for our local paper to hopefully solicit further funding for this good local cause.
   This camera system was donated in the name of PSUBS.org and was a good way I could see to promote our sport even though no actual submarine was ever involved.
   We have also donated hand held bullhorns to the local school in this way obtained from earlier transducer testing. The electronics when confined tended to overheat and thus were not of use to us. Calling kids to to the bus as school let out seemed a much better purpose for these.
 
   There may be things you may find unsuitable in the quest for things submarine that also could be used to promote good will in behalf of our sport in your local area. So before you let gather dust on a shelf or simply gets thrown away, give this some thought.
 
                                                                                                                               David Bartsch

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