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rgrrbt
Joined: 08 Jan 2011 Posts: 13
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Link Posted: Wed Jan 19, 2011 5:40 pm Post subject: fried my voltmeter - looking for troubleshooting tips |
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After working on my build off and on over the last two months, I turned the power on my control panel for the first time last night. The results were not what I had expected. I heard a pop, the face of the volt meter popped off and the display was smoked. The 7 amp fuse blew.
I thought I had followed the entire wiring schematic to a T (including the install of the safety interlock). Prior to turning on the power, I had measured resistance across the power supply receptacle's ground and both the control panel box and door, and ensured the enclosure was properly grounded.
I'm not really sure where to start troubleshooting. Any ideas?
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kal Forum Administrator
Joined: 12 Dec 2010 Posts: 11121 Location: Ottawa, Canada
Drinking: Pub Ale, Electric Creamsicle, Mild, Pliny the Younger, Belgian Dark Strong, Weizen, Russian Imperial Stout, Black Butte Porter
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rgrrbt
Joined: 08 Jan 2011 Posts: 13
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Link Posted: Wed Jan 19, 2011 6:28 pm Post subject: |
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Thanks Kal. I intend to go back through all of my wiring. The only thing I noticed initially is that I grounded the doorbell transformers given they each had a green ground wire on the 120v AC side. I didn't notice that in your wiring diagram, but I don't think that would have caused a short. Am I better off not grounding them?
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kal Forum Administrator
Joined: 12 Dec 2010 Posts: 11121 Location: Ottawa, Canada
Drinking: Pub Ale, Electric Creamsicle, Mild, Pliny the Younger, Belgian Dark Strong, Weizen, Russian Imperial Stout, Black Butte Porter
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rgrrbt
Joined: 08 Jan 2011 Posts: 13
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kal Forum Administrator
Joined: 12 Dec 2010 Posts: 11121 Location: Ottawa, Canada
Drinking: Pub Ale, Electric Creamsicle, Mild, Pliny the Younger, Belgian Dark Strong, Weizen, Russian Imperial Stout, Black Butte Porter
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rgrrbt
Joined: 08 Jan 2011 Posts: 13
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Link Posted: Wed Jan 19, 2011 6:57 pm Post subject: |
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Both transformers had 3 wires, they were identical to the transformer to which I linked. I am beginning to think the source of the short must be somewhere else.
Are there any typical culprits?
My volt meter was one of the 5-pin models about which there is another thread. It was a little confusing as to the wiring of each pin, but I thought that thread cleared it up. If I reversed the AC in and DC out threads, could that have resulted in a short and the fuse blowing?
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kal Forum Administrator
Joined: 12 Dec 2010 Posts: 11121 Location: Ottawa, Canada
Drinking: Pub Ale, Electric Creamsicle, Mild, Pliny the Younger, Belgian Dark Strong, Weizen, Russian Imperial Stout, Black Butte Porter
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rgrrbt
Joined: 08 Jan 2011 Posts: 13
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Link Posted: Wed Jan 19, 2011 7:16 pm Post subject: |
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While I follow that applying 240V AC directly to the voltmeter would fry it, I don't think it necessarily follows that reversing the AC and DC wires on the volt meter would have resulted in the fuse blowing. Does that make sense?
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kal Forum Administrator
Joined: 12 Dec 2010 Posts: 11121 Location: Ottawa, Canada
Drinking: Pub Ale, Electric Creamsicle, Mild, Pliny the Younger, Belgian Dark Strong, Weizen, Russian Imperial Stout, Black Butte Porter
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Link Posted: Wed Jan 19, 2011 7:23 pm Post subject: |
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rgrrbt wrote: | While I follow that applying 240V AC directly to the voltmeter would fry it, I don't think it necessarily follows that reversing the AC and DC wires on the volt meter would have resulted in the fuse blowing. Does that make sense? |
Just to be clear, when you say "reversing the AC and DC wires on the volt meter", do you mean reversing one AC wire with the other AC wire, and reversing the DC +5V wire with DC GND wire? That shouldn't fry anything I would imagine.
You can't reverse the AC anyway. It's not polarized.
Reversing the two DC wires would simply cause the meter to not work most likely. Certainly wouldn't cause more than 7A to be drawn through the fuse to pop it.
Kal
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rgrrbt
Joined: 08 Jan 2011 Posts: 13
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Link Posted: Wed Jan 19, 2011 7:33 pm Post subject: |
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I realize that there is no polarity to the AC side. What I meant was reading the pins backwards. Instead of wiring AC in to 1 & 2 and DC to 4 & 5, wiring DC to 1 & 2 and AC to 4 & 5.
This again leads me back to trying to hunt down a short circuit. I think my troubleshooting plan is to retrace all wires, comparing them to the schematics.
Is there any way to check for a short utilizing a multimeter? I know how to measure resistance and voltage, but given that the fuse blows and the breaker trips when power is supplied, I don't know how to go about doing that.
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kal Forum Administrator
Joined: 12 Dec 2010 Posts: 11121 Location: Ottawa, Canada
Drinking: Pub Ale, Electric Creamsicle, Mild, Pliny the Younger, Belgian Dark Strong, Weizen, Russian Imperial Stout, Black Butte Porter
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Link Posted: Wed Jan 19, 2011 7:44 pm Post subject: |
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rgrrbt wrote: | I realize that there is no polarity to the AC side. What I meant was reading the pins backwards. Instead of wiring AC in to 1 & 2 and DC to 4 & 5, wiring DC to 1 & 2 and AC to 4 & 5. |
Yes. Very bad as I mentioned above.
Quote: | This again leads me back to trying to hunt down a short circuit. I think my troubleshooting plan is to retrace all wires, comparing them to the schematics. |
Yup. Use your brain too! If for whatever reason one of the parts you used is slightly different than the one I documented with, the schematics may have to change slightly.
Quote: | Is there any way to check for a short utilizing a multimeter? I know how to measure resistance and voltage, but given that the fuse blows and the breaker trips when power is supplied, I don't know how to go about doing that. |
Most multimeters have continuity testers. That's just measuring for (close to) 0 ohms resistance. Most meters have a "beep" test. If there's a short it'll beep.
You don't want to test that with power on or the unit plugged in.
It may no longer be a short either if something blew however. That's the thing: If something was shorted, it likely no longer is since the part blew due to the excess current. I'm surprised that the part and the voltmeter both blew. Sounds like the voltmeter probably blew first with very low current and then later the 7A fuse blew. So sounds like you have a direct short somewhere (or did).
Testing/troubleshooting stuff like this is not something you can unfortunately teach easily, let alone remotely. As always electricity is dangerous, and so on.
Kal
_________________ Our new shop with over 150 new products: shop.TheElectricBrewery.com
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kal Forum Administrator
Joined: 12 Dec 2010 Posts: 11121 Location: Ottawa, Canada
Drinking: Pub Ale, Electric Creamsicle, Mild, Pliny the Younger, Belgian Dark Strong, Weizen, Russian Imperial Stout, Black Butte Porter
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rgrrbt
Joined: 08 Jan 2011 Posts: 13
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Link Posted: Wed Jan 19, 2011 9:49 pm Post subject: |
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Yes, I am using two of the variable DC power supplies and two doorbell transformers. Why do you ask? I read your comment on your main site about not being able to use a single DC power supply for both the volt and amp meter. Thank you for your efforts today in helping me being to trouble shoot this.
I'm going to check continuity of all of the switches and relays to ensure the other parts are still working.
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kal Forum Administrator
Joined: 12 Dec 2010 Posts: 11121 Location: Ottawa, Canada
Drinking: Pub Ale, Electric Creamsicle, Mild, Pliny the Younger, Belgian Dark Strong, Weizen, Russian Imperial Stout, Black Butte Porter
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kal Forum Administrator
Joined: 12 Dec 2010 Posts: 11121 Location: Ottawa, Canada
Drinking: Pub Ale, Electric Creamsicle, Mild, Pliny the Younger, Belgian Dark Strong, Weizen, Russian Imperial Stout, Black Butte Porter
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Link Posted: Wed Jan 19, 2011 10:05 pm Post subject: |
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The other option is that maybe there's something wrong with my diagrams!
Has anyone else wired up their amp/voltmeter and got them running fine? (Other than me?)
Did anyone follow the diagrams/instructions and notice an error and correct it without letting me know? (Shame on you!)
Conceptually it's really really simple:
Do you have the documentatin that came with your meters?
On the diagram I purposely labelled the inputs on the meters with what they "did" instead of saying "pins 1/2/3" so that people would have to confirm which pin to use.
I've also added a note to the page to confirm that the pinouts of the meters with the documentation that was supplied with them. Do not assume that (for example) the pins from left to right on the volt meeter are +5VDC, DC GND, AC, AC.
The manufacturer may have changed it. I have no way of knowing that.
Kal
_________________ Our new shop with over 150 new products: shop.TheElectricBrewery.com
We ship worldwide and support our products and customers for life.
Purchasing through our affiliate links helps support our site at no extra cost to you. We thank you!
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rgrrbt
Joined: 08 Jan 2011 Posts: 13
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Link Posted: Wed Jan 19, 2011 10:31 pm Post subject: |
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kal wrote: |
Do you have the documentatin that came with your meters?
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Unfortunately, mine did not come with any documentation. The amp meter appears to be identical. The voltmeter is different in that it has five pins. I believe it is the same as Goatbrewer's meter. He posted this link to documentation http://www.sure-electronics.net/measure,tools/panelmeter%20Vot-new.pdf
When the pin number is referred to that is the male pin and not the female receptacle, correct?
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rgrrbt
Joined: 08 Jan 2011 Posts: 13
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Link Posted: Wed Jan 19, 2011 10:34 pm Post subject: |
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kal wrote: | Check for shorts from the DC power supplies to the backplane too. I had to use little offsets to make sure the backsides weren't shorting against the backplane. |
While I did use the rubber washers as shims, I will go back and check for a short there. Perhaps the shims I used weren't thick enought.
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kal Forum Administrator
Joined: 12 Dec 2010 Posts: 11121 Location: Ottawa, Canada
Drinking: Pub Ale, Electric Creamsicle, Mild, Pliny the Younger, Belgian Dark Strong, Weizen, Russian Imperial Stout, Black Butte Porter
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rgrrbt
Joined: 08 Jan 2011 Posts: 13
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Link Posted: Fri Jan 21, 2011 3:19 am Post subject: |
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I think I found at least part of the problem. The pins on my voltmeter are different than those on goatbrewer's meter, even though they are both the same model number ML-5135!
While his have the AC inputs at pins 1 and 3, mine have the AC inputs at 4 and 5.
Shame on me for not opening the meter to verify before I wired it based on the manual he linked to in his thread here:
http://www.theelectricbrewery.com/forum/viewtopic.php?t=24563
However, I would have thought that the pins would have been consistent from model to model.
I think the lesson learned from which others may benefit is to make sure one opens the meter and verifies the pin configuration for his or her specific meter. The manufacturer clearly has variability from unit to unit. Perhaps a warning like this should be added to the main site on the volt meter wiring page.
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