How to obtain QSI PowerGuard?

[jimhaleyscomet]

I have an old ZW that I am using to run modern locomotives.  Does anyone know where I can get QSI PowerGuard or some other Voltage Surge Surpressor / Circuit Breaker?  I keep replacing 15 amp fuses when the cat derails the train but that is getting old.  I have tried google search but not come up with anything. 

Jim H

[lionelsoni]

Here is an old topic that discusses TVSs in some detail:

http://www.trains.com/trccs/forums/2/740607/ShowPost.aspx#740607

Here is a data sheet from a manufacturer listing TVSs of various voltage ratings:

http://www.centralsemi.com/leadedpdf/1.5CE6.8CA-400CA.PDF

You should get one for which the VRWM is the highest peak voltage that you plan to use.  The peak voltage is 1.4 times the RMS voltage.  Be sure to get one with the CA suffix, which means bidirectional (for AC applications).  You can get one from Mouser for less than $1.

[jimhaleyscomet]

Thanks for the part number and link.  I ordered a bunch today...enough for all my transformers both new and old!

It appears from previous conversations that these should make my electronic boards last longer.  We can hope!

Jim Haley

[cheech]

bob

please exuse my non-electician and imprecise words....

when there is a spike and the diode begins its work, how do you know---is there a sound or does everying come to a stop on the rails or is it all transparent and everything keeps chucking? 

Secondly, after an 'event' do you need replace the diode? how do you know they are doing their job..is there a test.

thanks

[lionelsoni]

It is, as you say, "all transparent".

You should not need to replace the device; but that is a good point about knowing whether the thing is working, which I had not thought about before.  Off the top of my head, I can imagine a test set that you could build, something like a small power transformer with a higher-voltage output than normal for trains, with a pair of paralleled lamps, each with a diode in series, all in series with the transformer output.  The lamps would light to show that the track is protected for either polarity of spikes.  However, you would have to operate this thing with all the trains and other loads off the track.  Maybe someone else can suggest a simpler way to test TVSs.

[waltrapp]

I have a few QSI PowerGuards and one QSI PowerProgrammer.  When a spike occurs there is a red LED on the PowerGuard that blinks.

Nothing needs reset after what someone referred to as an 'event'.  I have had mine for 5 or 6 years now.  Of course, I have to qualify that and say that my layout is only up for 2 months each year.

- walt

[chuck]

http://www.hirailers.com/technical.htm#Surge%20Protector


Reprint from Hi Railers Buzz technical newsletter:

http://www.hirailers.com/surgepro1.pdf

[lionelsoni]

That's very interesting, Chuck.

I don't understand the reference to the Z4000; but I don't think I need to.

The circuit for detecting spike-suppression events looks like it should work; but I wonder whether it can't be made a little simpler.  I notice that the added diodes could be implemented with a single bridge-rectifier module, such as has been discussed numerous times on this forum.  Two diode pairs in series, as shown, is ample to turn on the 2N2222; but 4 diode pairs (two bridge rectifiers) would provide enough voltage to light red LEDs directly, wired back-to-back for reverse-voltage protection and then in series with a single small ballast resistor, perhaps 33 or 100 ohms.

I'm not sure that this completely does the job.  If you see a flash on an LED, you know that the TVS has suppressed a spike; but, if you don't see flashes, you don't know whether it is because spikes are not occurring or because the TVS has failed.  You would still have to try to put high voltage onto the track to verify that the TVS is intact, after taking the trains off first, of course.