AC/DC Generator with DPDT Switch?

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Old 09-14-11, 07:42 AM
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AC/DC Generator with DPDT Switch?

Hi. I'm desperately looking to buy an AC/DC power supply with a double-pole double-throw switch, but can't seem to find one for sale anywhere online. I have found plenty of "rectifiers" and "switching" AC/DC generators, but none specifically say they have a DPDT switch. I'm not too familiar with this (it's for an experiment), so I'm not sure if "switching" is the same as DPDT or not.

I know they exist.... here is an example of exactly what I need (just the generator, not the motor): K4-24.HTML

Any tips would be appreciated!
 
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Old 09-14-11, 09:36 AM
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Why can't you buy the switch separate. Your link actually seems to show a crude double blade knife switch. Generators are sold for specific purposes and will be primarily AC or DC though home AC generators may also have a 12v DC output for charging batteries but they will be called AC generators.
 
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Old 09-14-11, 11:10 AM
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Thanks. I'll buy a switch separately if I have no other choice, but I'd prefer not having to rig anything - for one, I'm not really sure what I'm doing, but also, I'm wondering if it could void my warranty on the generator.

I'm really just looking for a ready to go setup.
 
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Old 09-14-11, 11:17 AM
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I'm not really sure what I'm doing,
What do you think you are trying to do? Is this one of those get electric free scams from the net?
 
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Old 09-14-11, 11:28 AM
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Without going into too much detail, I'm using it to clean tarnish off of specific type of silver. The anode and cathode has to be reversed repeatedly during the cleaning process. It's been proven to work perfectly for what I need, using a AC/DC supply with a DPDT switch... the problem is acquiring the necessary equipment.

Can anybody else help?
 
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Old 09-14-11, 11:41 AM
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Ray wasn't calling you a scam artist...he was referring to the things you see all over the internet for these kinds of free power inventions. We get plenty of questions from folks wanting to build the machines advertised and try to dissuade them from wasting time and money.

Sorry...but w/o detail...it's going to be pretty hard for anyone to suggest options I imagine. A switch is just a switch, you can easily wire one in to a P/S to do whats needed. I've never seen any sort of P/S or generator that allowed you to reverse DC polarity with a panel mounted switch and I worked with plenty of power supplies in 24yrs of electronics in the Navy. Since AC has no polarity...that's not an issue.

I'm confused when you say you need an AC/DC supply......do you mean AC output with a floating DC voltage as well...on the same line? Or 2 separate outputs?
 
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Old 09-14-11, 11:46 AM
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How often do you have to reverse polarity of the DC? Is the AC used for anything?
 
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Old 09-14-11, 11:52 AM
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Originally Posted by Gunguy45 View Post
Ray wasn't calling you a scam artist...
I know - I realized that (too late) and deleted my comment! Sorry, Ray.

Originally Posted by Gunguy45 View Post
I've never seen any sort of P/S or generator that allowed you to reverse DC polarity with a panel mounted switch...
Did you see the link I provided in my first post? Isn't that setup what you are saying you've never seen before? I'm not being a smart***, it's a serious question. But I do know that if I could get exactly what is shown in the link in my first post, I'd be all set. They got theirs from somewhere - the frustrating thing is, I can't find one for myself. By the way, I emailed them for help but my message bounced.
 
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Old 09-14-11, 11:56 AM
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Originally Posted by belgarid View Post
How often do you have to reverse polarity of the DC? Is the AC used for anything?
According to the instructions I've read, the polarity needs to be manually reversed as needed, probably every few minutes or so. It's for electrolytic cleaning of silver, which involves repeated swapping of an anode and cathode. To my understanding, that's what the DPDT switch accomplishes.
 
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Old 09-14-11, 12:19 PM
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Oh...I saw the link...but thats nothing more than a demonstration rig for a science class. Built from a DC power supply, a special exposed motor on a base and an old style knife switch. Notice how its all connected with wires using alligator clips and such? It even says "Reversing the switch twice per rotation of the coil mimics an AC power source."...so it's just a DC supply with the polarity being reversed by the switch.

I don't really think you need a generator as such...just a DC supply that meets the requirements of whatever instructions you are reading. Heck..it could be a battery bank for that matter. Then you use the switch to change the polarity after wiring each side mirror of the other.
 
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Old 09-14-11, 12:25 PM
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Referring to the link what is pictured is a DC power supply, a switch of some sort and a demonstration motor used for teaching. It bears only little relevance to what you want to accomplish, removing tarnish from silver by some kind of electrolytic action.

Belgarid asked an important question, how often do you need to reverse the polarity? If it is only once an hour or once every several hours then simply reversing the wire connections is the easiest method. If it is more often, then a double pole, double throw switch is easier and if it is every few minutes then a timer and relay will be the most practical. In any case, the relevant parts are the DC power supply, connecting wires and (maybe) the switch. The motor is not necessary and I don't think you need any AC current in the process either.

So it boils down to your needing a (relatively) low voltage DC power supply, most likely with a variable voltage output. Before making any recommendations I would need to know the required current flow and voltage necessary for the process. If you don't know these then at least give me an educated guess or a reference back to where you got the original idea.
 
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Old 09-14-11, 12:33 PM
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Originally Posted by Gunguy45 View Post
Oh...I saw the link...but thats nothing more than a demonstration rig for a science class. Built from a DC power supply, a special exposed motor on a base and an old style knife switch. Notice how its all connected with wires using alligator clips and such? It even says "Reversing the switch twice per rotation of the coil mimics an AC power source."...so it's just a DC supply with the polarity being reversed by the switch.

I don't really think you need a generator as such...just a DC supply that meets the requirements of whatever instructions you are reading. Heck..it could be a battery bank for that matter. Then you use the switch to change the polarity after wiring each side mirror of the other.
Yeah, the silver cleaning process uses alligator clips too: one clip attached to the silver (the cathode), and the other attached to an anode.

I see what you're saying... and I considered not buying a fancy generator, but since it is what was recommended in the instructions, I thought I'd just play it safe and follow their instructions exactly, and not experiment too much. The stuff I'm working on is very delicate and potentially very valuable, and the voltage output has to be as precise as possible or it could irreversibly damage the item.

Well, thanks. I'll look into manually installing a switch onto a DC generator...
 
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Old 09-14-11, 12:40 PM
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Originally Posted by Furd View Post
So it boils down to your needing a (relatively) low voltage DC power supply, most likely with a variable voltage output. Before making any recommendations I would need to know the required current flow and voltage necessary for the process. If you don't know these then at least give me an educated guess or a reference back to where you got the original idea.
Thank you for your help. Yes, I need a low-voltage power supply with an adjustable output of between 1.5 and 5 volts. A manual switch is necessary because the switching needs to be done by eye, as needed, depending on the results of the cleaning. I'm estimating once every 5 minutes or so in a 20-30 minute session.
 
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Old 09-14-11, 01:00 PM
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Here is a relatively inexpensive power supply that has both constant voltage an constant current adjustments with digital displays. The upper voltage limit is a bit more than you specified and since you didn't specify a current it may not be sufficient in that respect.

0-30V,0-3A Mini Bench Supply-MPJA, Inc.

You can use just about any DPDT switch or you could just connect your wiring to a double banana plug and pull it out of the power supply, invert it and plug it back in as required thereby reversing the polarity.

BLACK DUAL BANANA PLUG-MPJA, Inc.

If you would rather have a knife switch here is one from MPJA that is currently out of stock but it gives you an idea of what is available.

DPDT MINI KNIFE SWITCH-MPJA, Inc.

(I have no relationship with MPJA other than as a satisfied customer.)
 
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Old 09-14-11, 02:32 PM
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I'll look into manually installing a switch onto a DC generator
As has been detailed above you do mot need a DC generator. You need a DC power supply. If you could give us a link to the article you are basing this on or scan and upload it to a hosting site we might be able to help more.

I considered not buying a fancy generator, but since it is what was recommended in the instructions, I thought I'd just play it safe and follow their instructions
I'd strongly question if the person who wrote that knew what he was talking about or it was a very poor translation from another language or from back in the days before solid state rectifiers when sometimes a motor generator set was more practical then vacuum tubes.
 
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Old 09-14-11, 02:50 PM
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Originally Posted by ray2047 View Post
As has been detailed above you do mot need a DC generator. You need a DC power supply. If you could give us a link to the article you are basing this on or scan and upload it to a hosting site we might be able to help more.

I'd strongly question if the person who wrote that knew what he was talking about or it was a very poor translation from another language or from back in the days before solid state rectifiers when sometimes a motor generator set was more practical then vacuum tubes.
I believe the link in my first post called it a generator - whether that was right or wrong, that's where I got it from, and not from the original instructions. Here are the part of the instructions that explain what I'm trying to accomplish. I've also seen video done of the process and read about it at other sources - it definitely works. I just could not find any detailed instructions on where to get all of the equipment:

Electrocleaning: place the silver piece into the holder apparatus and submerge in
an ammonium hydroxide bath (two parts water and one part ammonium hydroxide)
with at least one-inch coverage of solution. The holder is connected to a direct
current power supply whose voltage can be adjusted. Starting voltage should be about
two volts but can be increased to a maximum of five volts. A silver wand electrode
that is also attached to the dc power supply through a double-pole-double-throw
switch becomes the cathode and the silver piece is the anode in the first switch
position and the second switch position the reverse is true with the silver piece as
the cathode and the silver wand the anode. The silver wand is passed over the
silver piece in the solution above but not touching the corroded areas of the
surface. When the silver piece is in the cathode position, the applied voltage form
silver oxide thin films on the surface of the silver piece.. The silver oxide film is extremely
unstable due to its thinness, its solubility in the ammonium hydroxide solution and the
pH 12 measurement of the electrolyte solution. When the polarity is reversed, the
silver ions are reduced to silver and the tarnish is lifted from the
surface. This switching of anode and cathode is repeated until there is no
longer any visible tarnish removal or additional improvement in the appearance of the
silver piece.


Furd: Thanks again for your help. I'll be looking more into your links. I'd prefer the knife switch, but want to avoid having to do any wiring, if possible.
 

Last edited by Boston567; 09-14-11 at 03:14 PM.
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Old 09-14-11, 03:12 PM
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A generator would work as it produces DC current. This would be a lot more complicated then using a solid state DC power supply as Furd has stated. What you would need for this type of generator is an AC motor to turn the generator and then you would need a variable DC voltage to power the field windings in the generator to control the output voltage. You can accomplish the same thing by using a DC power supply without any of the other moving parts required.

If you don't want to use a knife switch you could use a 4-way light switch to swap the polarity.

The only question is how much current (amps) you will need for this. This would dictate the size of the DC power supply you would need.
 
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Old 09-15-11, 07:11 AM
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Well, I've decided I'm going with this power supply:
Amazon.com: MASTECH HY1803D VARIABLE DC POWER SUPPLY: Electronics

And this lead set:
Amazon.com: Banana to Large Alligator Lead Set: Micro-Tools

Will it work? I have no idea.

I'm also not sure what I'm going to do about the most important issue, the DPDT thing. I looked at banana plugs, but am not 100% sure how they work, really. I understand the concept, but do the lead ends plug right in to the banana plug, or do they have to be stripped first?

Then there's the issue of finding a silver electrode of some sort...
 
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Old 09-15-11, 07:53 AM
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I looked at banana plugs, but am not 100% sure how they work, really. I understand the concept, but do the lead ends plug right in to the banana plug
You plug them into the jacks on the front of the power supply. Seems expensive just for a test. You could put what you need together for less then $20 with a 6 volt lantern battery and a 4-way light switch.
 

Last edited by ray2047; 09-15-11 at 11:24 AM.
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Old 09-15-11, 07:56 AM
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The leads should plug right into the jacks on the front of the power supply. You would then connect the alligator clips to the electrodes. To reverse power, just swap the location the leads are plugged into. Normally you would put the red lead into the red plug and the black plug into the black plug. The red on the power supply is the positive. So, to reverse current, just reverse the leads, place the black lead into the red plug and the red lead into the black plug.
 
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Old 09-15-11, 10:46 AM
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I guess you have more money than I. Why are you planning on spending an extra $20 for the power supply from/through Amazon plus shipping AND state sales tax instead of the power supply I recommended?

Where in Washington state are you located?
 
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Old 09-15-11, 11:02 AM
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I have a $500 budget for this project, so an extra $20 or so isn't going to kill me. The main reason I am going through Amazon is because I get a special discount there plus free 2nd Day air shipping. So it's not nearly as bad as it seems. Thanks for your recommendation though; it led me to find what I was looking for on Amazon. And I'm about 20 miles NE of Seattle.

Also: Thanks for the clarification, belgarid.
 
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Old 09-15-11, 11:06 AM
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Originally Posted by Boston567 View Post
And I'm about 20 miles NE of Seattle.
Not far from me, I live in Bothell.
 
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Old 09-15-11, 11:08 AM
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Originally Posted by Furd View Post
Not far from me, I live in Bothell.
Small world. I lived in Bothell for about 9 years. Just moved out here to E. Woodinville.
 
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Old 09-15-11, 11:41 AM
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Try the coin dealers for a "wand". Ask if they have any old pre 1935 silver dollars or pre 1964 half dollars rated poor condition. You should be able to get them for the cost of the silver. You can then epoxy it to a short length of PVC pipe. While they are only 90% silver my guess is they would work.
 
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Old 06-27-14, 10:07 AM
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Hi,
I am also thinking about electrocleaning daguerreotypes. Were you successful in obtaining the necessary equipment to attempt the electrocleaning process? If so, how well did it work?
 
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Old 06-27-14, 11:12 AM
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The OP hasn't been back to this site for almost 3 years.
 
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Old 06-27-14, 11:24 AM
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Welcome to the forums.

dc..... electrocleaning daguerreotypes is a highly sophisticated job as the picture itself is actually on the metal and can be very easily ruined. You would be best served in finding a forum where they specialize in that exact work.


If you would like to persue your request at DIY...... you should start a new thread and use this one as a reference.
 
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