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rgrrbt
Joined: 08 Jan 2011 Posts: 13
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Link Posted: Sat Jan 08, 2011 4:36 am Post subject: volt meter wiring |
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Kal, in the wiring diagram posted on The Electric Brewery site, you indicate both 14 gauge Hot A and Hot B going into the back of the volt meter. How did you wire this given the pin socket that is included with the volt meter appears to be 22-24 gauge?
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kal Forum Administrator
Joined: 12 Dec 2010 Posts: 11123 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: Sat Jan 08, 2011 9:56 pm Post subject: |
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14 ga is pretty small. It may fit. You can cut off some of the strands to make it fit if you want, or solder on a little piece of solid core 22ga wire and put on some really small heat shrink tubing to cover up the solder point to ensure you don't get shorts. That's what I did.
Here's a pic:
Kal
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crush
Joined: 28 Dec 2010 Posts: 706 Location: Telemark, Norway
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Link Posted: Sun Jan 09, 2011 12:14 am Post subject: |
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[Deleted: double post]
Last edited by crush on Sun Jan 09, 2011 12:28 am; edited 1 time in total
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crush
Joined: 28 Dec 2010 Posts: 706 Location: Telemark, Norway
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Link Posted: Sun Jan 09, 2011 12:27 am Post subject: |
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I've been wondering why we need two transformers, and if someone can explain exactly what is isolation and why it's necessary here. I'm wondering why the variable transformers themselves don't provide isolation, but having 2 doorbell transformers does?
Which device is it that need isolating, the voltmeter or ammeter? I'm hoping to power many low current 12v devices, so I hope they can all come from the same power supply and just use one extra supply for the "rogue" unit.
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crush
Joined: 28 Dec 2010 Posts: 706 Location: Telemark, Norway
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Link Posted: Sun Jan 09, 2011 12:30 am Post subject: |
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Can't we use 22 gauge for the meter - surely the current drawn is in milliamps?
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kal Forum Administrator
Joined: 12 Dec 2010 Posts: 11123 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: Sun Jan 09, 2011 2:26 am Post subject: |
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crush wrote: | I've been wondering why we need two transformers, and if someone can explain exactly what is isolation and why it's necessary here. I'm wondering why the variable transformers themselves don't provide isolation, but having 2 doorbell transformers does?
Which device is it that need isolating, the voltmeter or ammeter? I'm hoping to power many low current 12v devices, so I hope they can all come from the same power supply and just use one extra supply for the "rogue" unit. |
One of the AC inputs on the volt meter is tied to the DC ground so separate power supplies are needed.
crush wrote: | Can't we use 22 gauge for the meter - surely the current drawn is in milliamps? |
You make a good point. You can. I've changed the picture. It can all be 22 ga.
Kal
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crush
Joined: 28 Dec 2010 Posts: 706 Location: Telemark, Norway
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Link Posted: Sat Feb 05, 2011 1:41 pm Post subject: |
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kal wrote: | crush wrote: | I've been wondering why we need two transformers, and if someone can explain exactly what is isolation and why it's necessary here. I'm wondering why the variable transformers themselves don't provide isolation, but having 2 doorbell transformers does?
Which device is it that need isolating, the voltmeter or ammeter? I'm hoping to power many low current 12v devices, so I hope they can all come from the same power supply and just use one extra supply for the "rogue" unit. |
One of the AC inputs on the volt meter is tied to the DC ground so separate power supplies are needed.
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After some research and thinking, I believe I see why isolation is needed and how this is provided by the transformer.
I think it's something like this: with the 120v AC and DC ground wired together in the voltmeter, any return path to AC will allow 120v to flow through the DC side of the circuit. When a transformer is used, there is no return path, since the input / output coils are entirely separate and there is no path to complete a 120v circuit. Using a switched power supply would not work, since there is an electrical connection between the output and the input, allowing 120v to flow.
But what I don't understand is why two transformers are needed. Can someone correct my thinking and explain exactly what happens with one transformer that causes the circuit to blow?
Thanks,
mat.
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crush
Joined: 28 Dec 2010 Posts: 706 Location: Telemark, Norway
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Link Posted: Mon Feb 07, 2011 2:05 pm Post subject: |
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I just noticed on my ammeter that the instructions also say that this has the dc ground wired to a 230v input, so both the ammeter and the voltmeter have this feature. So now I see why both need isolating. In principle, it's possible to have just one transformer, but you have to be 100% certain that the the 230v that is tied to the dc ground is the same polarity on both meters. If they are opposite polairty, then a circuit is formed and 230v will flow through the dc side of the circuit. So, it's simplest just to have two transformers where this cannot happen.
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kal Forum Administrator
Joined: 12 Dec 2010 Posts: 11123 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: Mon Feb 07, 2011 2:10 pm Post subject: |
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crush wrote: | So, it's simplest just to have two transformers where this cannot happen. |
Hence the reason I used two transformers.
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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crush
Joined: 28 Dec 2010 Posts: 706 Location: Telemark, Norway
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Link Posted: Mon Feb 07, 2011 3:07 pm Post subject: |
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kal wrote: | crush wrote: | So, it's simplest just to have two transformers where this cannot happen. |
Hence the reason I used two transformers.
Kal |
Hehe! Yes, simplest is best. I just wanted to understand exactly why it was necessary.
I'll be using two transformers also. Safely using just one requires opening up both meters to see which AC input is tied to ground in each, and making sure both of those have the same polarity. Too much hassle!
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kal Forum Administrator
Joined: 12 Dec 2010 Posts: 11123 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: Mon Feb 07, 2011 3:18 pm Post subject: |
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Yup. Maybe not too much hassle for someone who knows what they're doing but for my instructions I have to go the 'safe' way since not all meters may be the same and I didn't want to have to give all sorts of complicated instructions for people to just save $10. I also did not want to assume that people would be buying the exact same meters as me.
You also don't want to have to re-think the wiring if every you decide to replace a part. The system should be build somewhat generically to minimize reliances between parts.
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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