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EETimes Puzzle: Mystery MOSFET Loads

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zeeglen
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Re: Whattup? What was the conclusion? ;-)
zeeglen   7/10/2014 7:25:13 PM
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@ Lee

Answers are in Part 2 here:

http://www.eetimes.com/author.asp?section_id=36&doc_id=1322984

Max, could you insert a link in Part 1 to get to part 2?

studleylee
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Whattup? What was the conclusion? ;-)
studleylee   7/10/2014 5:35:51 PM
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Hi, just wanted to know if an answer was posted.

Thanks, -Lee

studleylee
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I guesss...
studleylee   7/3/2014 6:28:08 PM
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Q's drive inductive loads probably relays or bulbs . They have snubbers and flyback protection for HV( 120v-ish loads commened to a positive rail ).

Alarm is logic sum of 2 peaking detectors if either 'load voltage at Q's' doesnt toggle during the rc time constant, the alarm will activate( active low).

555 tau ~ which would tell the expected timeout tested for.

-Lee Studley ( edited this a couple of times :-)

Wnderer
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Re: Puzzle
Wnderer   7/3/2014 9:48:30 AM
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@eetcowie

I don't see why you would need to prevent the two transistors from turning on at the same time in a motor. I think a two phase motor would have its coils driven 90 degrees out of phase not 180 degrees.

Yvon.H
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Re: What could it be?
Yvon.H   7/3/2014 7:56:28 AM
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It looks to me as a circuit to drive a ring signal from a telephone station based on the 48V, the frequency and the output voltage. 

 

Navelpluis
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Driving a small transformer
Navelpluis   7/3/2014 4:51:30 AM
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As seen from the protection stuff on the outputs I think it is driving a small transformer, probably center tapped. This transformer is driving 2 nasty devices capable of giving a big burst of energy back to the primary drivers. It might be 2 enormous MOSFET's or IGBT's that -depending on the speed and load- are able to destroy direct logic driving. I think at least I should win half a pint of lukewarm beer....(Yikes! ;-)

zeeglen
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Re: Aha! It's a trick question!
zeeglen   7/2/2014 8:28:33 PM
@betajet My other off-beat guess is a flipper torpedo, with a single tail fin powered by alternating electromagnets.

This would be great if used on one of those helium-filled air-floating sharks that Max wrote about a while back.  The 400 Hz tone would be a bit annoying, but at least would give warning that the beast was approaching - from miles away!  And could also double as a fire alarm bell if two gongs were located near the tailfin.  :^}

As for the red connection points, thay are just part of the net naming symbol in TinyCAD schematic drawing software.  One has to position the red connection point on the wire to give it a name, so there really is a connection.

 

betajet
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Aha! It's a trick question!
betajet   7/2/2014 2:22:20 PM
If you look closely at the schematic, you'll see that the connection points on the four off-page connectors are red, which means they're not actually connected.  [PCB designer rule #1: never trust the schematic.  Always check the netlist!]  This means there's no power in, no connection to loads be they inductive or otherwise, and no connection to ~Alarm.

Actually, I'm going to go with a couple of off-beat guesses.  Since the input voltage is +48V, that sounds like four 12V batteries, which is a common configuration battery back-up of serious electronics.  I'm guessing a really loud alarm bell, actually a pair of bells with a hammer between them which is driven by two electromagnets alternating at 400 Hz.  I mean really loud, the kind of alarm that clears a building in case of fire.

My other off-beat guess is a flipper torpedo, with a single tail fin powered by alternating electromagnets.  The reason for a flipper rather than a circular propeller is so that it has a passive sonar signature that sounds like a fish.

jmumford913
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Re: What could it be?
jmumford913   7/2/2014 2:07:17 PM
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I'm going to guess, based on the 110V zener diodes in the output, that the load is around 45mA (since that's what the zeners are going to be conducting when the JFETs are off and the opposite rail is active).

antedeluvian
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Re: Puzzle
antedeluvian   7/2/2014 12:55:02 PM
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Ivan

The alarm goes low whenever the pulsing AC voltage quits on either EdgeConn1 and/or EdgeConn2. This means that if the 555 fails, or the external inductors blow open, or the external voltage being supplied from somewhere to the inductor-loads (may not be the same 48v+ supply) fails, then the alarm goes low (asserted).

That makes much more sense. I missed that red bar over the ALARM.

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