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Low voltage AC/DC Adapter

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14 hours ago, TheDucks said:

This kind of thing was a Radio Shack item.  We have Fry's out here :/ for parts (if they restock).

Jameco (in San Carlos, CA) is good for Mail order

You want at least 25V. 35V is great headroom

https://www.amazon.com/dp/B015O7O068/ref=sspa_dk_detail_3?psc=1&pd_rd_i=B015O7O068&pd_rd_wg=fIiSH&pd_rd_r=Q0EGKYQDV51YWDDF5PZ0&pd_rd_w=Pr2Jh

The CMB24D is specified at a maximum 30 VDC input.  From personal experience hacking some LED wreaths, the input regulator without a heat sink gets burning hot at 29 VDC.  And if his lights are 12 volts, anything much above will be an issue.

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1 hour ago, Orville said:

Here's the same FWDB's I found at Radio Shack but MUCH CHEAPER!

http://www.mpja.com/1A-50PIV-DIP-Bridge-Rectifier/productinfo/25225+BR

The above url is an IC style FWDB and is Printed Circuit mount..

http://www.mpja.com/4A-50PIV-In-Line-Bridge-Rectifier/productinfo/25237+BR

Any of these could be used for low voltage AC to DC conversion.  

BTW: these things can also go the other way too, they can also convert low voltage DC adapters or even Batteries to AC by connecting the DC adapters or Battery + output to the + on the FWDB, the DC adapters or Battery - output to the - on the FWDB and you'll get AC out at the ~ markings on the FWDB.  I've done this if I needed to power an low powered AC device or just needed AC from a battery connection where an electrical outlet was unavailable or not plausible.

Please keep in mind the current rating - 4A may be to small for a bunch of landscape lights.  The 25A version you linked to from Radio Shack would probably be OK.

As to your comment about a bridge rectifier turning DC into AC - the laws of electronics make this impossible.  The + side of a bridge has 2 cathodes connected to it, blocking current flow to the ~ terminals.  In a similar fashion, the - side of a bridge has two anode connections.  You need a DC to AC inverter to get AC from a DC source.

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20 hours ago, radioguy1007 said:

The CMB24D is specified at a maximum 30 VDC input.  From personal experience hacking some LED wreaths, the input regulator without a heat sink gets burning hot at 29 VDC.  And if his lights are 12 volts, anything much above will be an issue.

35V is the next standard RATING above 25V.  Like the CMB24, capacitors have Max Ratings also.  35V does not mean it makes 35V out of thin air.

that lighting pak is 12V RMS.  a 'magic number used in full wave AC to DC rectification: 1.414    (the reason I also recommended a BUCK regulator)

Since the pak is also unregulated  (Sola type lighting paks would be horrendously expensive for a typical application that usually has a wide tolerance)

 

 

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21 hours ago, radioguy1007 said:

Please keep in mind the current rating - 4A may be to small for a bunch of landscape lights.  The 25A version you linked to from Radio Shack would probably be OK.

As to your comment about a bridge rectifier turning DC into AC - the laws of electronics make this impossible.  The + side of a bridge has 2 cathodes connected to it, blocking current flow to the ~ terminals.  In a similar fashion, the - side of a bridge has two anode connections.  You need a DC to AC inverter to get AC from a DC source.

Then explain why I have been able to put a multi-meter across the tilde "~" terminals of an Full Wave Diode Bridge and gotten an AC current out of them?  So, yes, it is possible to convert DC to AC using one, done it many times on low powered AC motors that won't work off DC doing this.   All I know is it does work. 

If I put the multi-meter on DC at the ~ outputs, depending on the multi-meter, I get overflow error or no voltage reading at all, I put the tester on the AC voltage check and get a reading of the AC voltage I expected using the 12VDC or 24DC adapter power I put through the +/- terminals of the FWDB.   Again, it's always worked and I've powered a lot of low powered AC devices in this manner.   

Never once had an issue with doing this inversion this way.  Would not recommend it for any high powered devices, just small things that operate from from 5VAC to 24VAC.  

Had a 24VAC motor that controlled an animatronic item, motor would only work on AC, tried DC and it would not work with a 24VDC motor, put in a FWDB, wired the 24VDC adapter through the FWDB + to + and - to - on the FWDB and DC adapter, tested it on the animatronic, ~AC~ motor ran fine and it worked, getting 24VAC output from that 24VDC adapter at the ~ marks on FWDB.  So as far as I know, it works and can be done.  Been using this with this animatronic that operates for 10-12 hours a day through the holidays for years, again, no problems or issues.    It works for me, maybe your mileage is different on this, but it shouldn't be.

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Simple:  it is DC leakage.   The AC (setting) input gets rectified and the resistors adjust for average RMS (there are a few True RMS reading meters. They cost more)

There are very few multi-meters that have a DC blocked input (labeled Output) like the old Simpson 260/270 did

Edited by TheDucks

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On 6/2/2018 at 1:19 PM, TheDucks said:

Simple:  it is DC leakage.   The AC (setting) input gets rectified and the resistors adjust for average RMS (there are a few True RMS reading meters. They cost more)

There are very few multi-meters that have a DC blocked input (labeled Output) like the old Simpson 260/270 did

Then why does it work to power ~AC~ motors that I've tried to power from DC voltage and they won't even power up on DC{?}, but I run them through the full wave diode bridge and they run.   Seems if this was just "DC leakage", these ~AC~ motors would still NOT run, but they do.  Just know it works and as long as it does, I'll keep doing it when I don't have or can't find the AC voltage adapter I may need to do the job.

Edited by Orville

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There is something you are not telling us.  A full wave bridge rectifier absolutely positively can NOT produce AC power from a DC input (for several reasons).

Now I will point out that a LOT of hand power tools will run on either AC or DC equally well provided you give them the right voltage because of the motor design.  However most of those are 120 volt and won’t do much of anything on 12 volt (AC or DC).

Post a video...

 

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Brush type motors are usually Universal. AC/DC  Some motors are really DC, but include internal rectifiers to allow AC suplies.

I am totally with K6CCC.   No way will a bridge create AC

I am a graduate of the US Navy Electronics (Radar) schools with 50 Years pushing Trons under my belt  :D

 

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AC means alternating current and has a frequency that it changes, specified in Hertz.  The US standard line frequency is 60 Hertz.  DC (direct current) has no frequency component, it is constant potential.  The only way to make a frequency from DC is to use an inverter that chops the DC into pulses.

As members above have stated, many small motors are universal type - they will have a commutator and brush assembly.  DC motors will have brushes - with the exception of stepper motors where the magnetic fields are electronically rotated about the rotor to make it spin.

I am an electrical / electronics design engineer with nearly 40 years of experience. 

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All I know is the motor would not function on DC, but works on AC, All I did was add a FWDB between the DC output of an DC adapter and connected the ~ markings on the FWDB to the motor and it makes the motor work.   Like stated, I don't know why it worked or works, but it does.  The only thing between the DC adapter and the AC motor is nothing but a FWDB, no other circuits, parts, etc.    Maybe it's just a fluke it worked, I don't k now.

And for the record, I worked in electronics for over 40+ years,  worked in prototype engineering labs as well as electronic technician, so I do know my way around circuitry.    But this one worked as stated, and it by the MM it is outputting AC at the ~ terminals on the FWDB.   Maybe it's not supposed to, but it is doing it or the motor wouldn't be running when I plug the DC adapter in, if I take out the FWDB between the DC adapter and the AC motor and connect the adapter straight to the motor, the motor will not run, won't do a thing off DC voltages directly, but works through the FWDB.  

Maybe there is something about this particular FWDB I have no idea about, it's one I scavenged from my used parts box I take out of other non-working devices. 

Looks like a basic FWDB to me, 2 ~ markings and a + and -, but who knows what may be inside it.   I just know this particular one makes the AC motor operate.   Since it worked first time, I never tried a different one to see if any other one would work.   Looks like I need to do some testing with some others and see if I get the same results, but I thought I'd read somewhere that low voltage AC was possible by using the + and - as inputs and that AC would be output from the ~ markings{leads} on FWDB's.

So now I'm thinking the FWDB I used may not be an FWDB at all, but possibly something else.  

It looked like a square with one side angled, has only 4 leads, 1 +, 1 - and 2 ~, but there is nothing stamped or written on the part it's completely blank, all the other FWDB's I have and know that's what they are marked..  And since it worked, I encapsulated it with a type of potting material to make it a permanent part of the animatronic device, so now I can't even get a photo to post of what it looks like to even try to possibly identify what it might be. 

But I thought for certain because of the markings, size and shape it was an FWDB, now I'm  not too sure what it could be.    Do they even make inverters the same size as an FWDB and would it only have 4 leads on it marked like an FWDB?  

I haven't kept up with the newer, smaller stuff in electronics for quite a few years now, so I'm not sure of what's all out there.

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A WOTG (Way out there Guess)   😜 😜    You created a ripple pass filter.

If you follow the conduction paths on a reverse wired bridge,  (DC on the + / - and  load on the ~  ) there is no way to get any difference voltage at ~

I wonder (since there are ZERO p/n markings) if you have a custom chopper module in a standard package.  just because I have never seen one of these beasts, does not prove  they don't exist.

(the bolt hole is to mount and add extra heat sink capability)

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On 6/6/2018 at 11:30 AM, TheDucks said:

A WOTG (Way out there Guess)   😜 😜    You created a ripple pass filter.

If you follow the conduction paths on a reverse wired bridge,  (DC on the + / - and  load on the ~  ) there is no way to get any difference voltage at ~

I wonder (since there are ZERO p/n markings) if you have a custom chopper module in a standard package.  just because I have never seen one of these beasts, does not prove  they don't exist.

(the bolt hole is to mount and add extra heat sink capability)

You might be on to something there.   It had a bolt hole, but it didn't look like plastic, it looked like it had a metal ring around the bolt hole, never tested it, but thinking that could also be a ground or just a design for when a heat sink is used to direct the heat to the heat sink and off the part itself.  

Now I wish I hadn't of potted it in so I could have gotten a photo of the thing to see if anyone could have possibly identified what it might be, if that would even be possible. 

I originally  did think it was odd that an FWDB would do that at first, but when it worked and I "thought" it was an FWDB, I came to the conclusion that it was possible to get AC out of one going through the +/- terminals.   And of course, there is also misinformation out here on electronics when looking up things on the 'net, so I'm sure I read it somewhere on the 'net that getting AC out of an FWDB was possible.    

Went and tried the link I had to go back and check out the material several different times and days, and guess what?, It's not there any longer, get the dreaded page not found error, so another url bites the dust in my large collection that was giving incorrect information.  

Guess someone with the correct knowledge got that info stripped off somehow.

When I find out something I've looked at like this has given me incorrect info, those urls hit the trash bin immediately. 

Just glad this was something LOW voltage I was working on and that it wasn't an actual FWDB, might have had some bad repercussions doing what I thought would work.

Next time, I'm going to ask the folks on the forums here before I make another blunder like this one that could have had some bad consequences! 

 

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2 hours ago, Orville said:

You might be on to something there.   It had a bolt hole, but it didn't look like plastic, it looked like it had a metal ring around the bolt hole, never tested it, but thinking that could also be a ground or just a design for when a heat sink is used to direct the heat to the heat sink and off the part itself.  

Now I wish I hadn't of potted it in so I could have gotten a photo of the thing to see if anyone could have possibly identified what it might be, if that would even be possible. 

I originally  did think it was odd that an FWDB would do that at first, but when it worked and I "thought" it was an FWDB, I came to the conclusion that it was possible to get AC out of one going through the +/- terminals.   And of course, there is also misinformation out here on electronics when looking up things on the 'net, so I'm sure I read it somewhere on the 'net that getting AC out of an FWDB was possible.    

Went and tried the link I had to go back and check out the material several different times and days, and guess what?, It's not there any longer, get the dreaded page not found error, so another url bites the dust in my large collection that was giving incorrect information.  

Guess someone with the correct knowledge got that info stripped off somehow.

When I find out something I've looked at like this has given me incorrect info, those urls hit the trash bin immediately. 

Just glad this was something LOW voltage I was working on and that it wasn't an actual FWDB, might have had some bad repercussions doing what I thought would work.

Next time, I'm going to ask the folks on the forums here before I make another blunder like this one that could have had some bad consequences! 

 

Back in the days of tube car radios, they had a 4 pin module called a Vibrator to chop (and switch) the 6 or 12VDC feed to a transformer to that raised the voltage to 200-300 V for the B+ supply.

(Here is a e-bay link for a picture https://www.ebay.com/itm/4-Pin-MALLORY-Auto-Radio-Vibrators-J12F-Type-6634C-RCA-110050-1-Untested-2-Pcs/392042053364?hash=item5b4786fef4:g:N7AAAOSw32lYv2lG )

These were mechanical switches, that vibrated back and forth.  The contacts, were switching Inductive loads, so the soon became pitted and the unit failed.  Along came the Transistor and some bright sole packaged an oscillator and a pair of switching transistors into the old package for a direct plug replacement.    I think you might have the modern version, sans transformer  ( chopper modules I googled, all have transformers)

 

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4 hours ago, TheDucks said:

Back in the days of tube car radios, they had a 4 pin module called a Vibrator to chop (and switch) the 6 or 12VDC feed to a transformer to that raised the voltage to 200-300 V for the B+ supply.

(Here is a e-bay link for a picture https://www.ebay.com/itm/4-Pin-MALLORY-Auto-Radio-Vibrators-J12F-Type-6634C-RCA-110050-1-Untested-2-Pcs/392042053364?hash=item5b4786fef4:g:N7AAAOSw32lYv2lG )

These were mechanical switches, that vibrated back and forth.  The contacts, were switching Inductive loads, so the soon became pitted and the unit failed.  Along came the Transistor and some bright sole packaged an oscillator and a pair of switching transistors into the old package for a direct plug replacement.    I think you might have the modern version, sans transformer  ( chopper modules I googled, all have transformers)

 

Yep, remember those old vacuum tube days of radio and tv.  Used to go with my dad to the local electronics store that had a tube tester and sold replacement tubes.  Know my dad was constantly replacing various tubes in those old tube powered tv and radios. 

That could very well be what it is, the modern version{integrated circuit} of those old vibrator tubes that raised and chopped voltages.

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