Really lost trying to figure this out

[lostintranslation]

I have this digital volt meter and it works,

http://www.ebay.com/itm/221293228404?ssPageName=STRK:MEWNX:IT&_trksid=p3984.m1439.l2649

but I needed to get one with higher impedance, so I got this one. my problem is figuring out if it will even work and how to wire it into the circuit.

http://www.jameco.com/webapp/wcs/stores/servlet/Product_10001_10001_2144606_-1

 

[KJ6EAD]

What circuit? I see no circuit here.

 

[lostintranslation]

I have a wiring diagram I have been working from, sorry, i don't have a circuit diagram, visuals make more sense to me, hence the lost in translation handle....edit: the diodes are history, and some of the resistors have changed, but the main part is still as is. and the yellow wire from the dvm goes to the pos cap terminal, even though the line goes through the neg line as well, it just was easier and quicker to draw. it only connects the pos cap term.

 

[KJ6EAD]

The original meter could operate on a supply from 4V to 30V but the new one needs 5V. Do you have that supply voltage available?

The original meter had an input impedance of 100k. No impedance is specified for the new meter.

The original meter could read input values up to 99V. The new one can only go to 200mV without modification. What makes you think this new meter is useful in your application?

 

[lostintranslation]

the original meter bleeds the caps slightly, about .1 volt per second, which I was trying to stabilize. the new meter has an impedance of 10M ohm, which I was working under the assumption would be a great enough impedance to stop the cap bleed down. the original and new meter both are on a 9 volt supply, so I thought that was right.

I am just trying to get the voltage reading without bleeding the caps.

 

[lostintranslation]

The PDF spec sheet on Jameco say that it can read 200V by selection joint soldering, or an add on board. so if I can get it to read even up to 100V, and have no bleed down on the caps, I am good. I have no clue about how to wire it into the circuit with more than 3 leads, like the old, which works and I understand how to wire it, and also, not sure what exactly I need to solder and un solder on "selection joints."....?

 

[jpanhalt]

the original meter bleeds the caps slightly, about .1 volt per second, which I was trying to stabilize. the new meter has an impedance of 10M ohm, which I was working under the assumption would be a great enough impedance to stop the cap bleed down. the original and new meter both are on a 9 volt supply, so I thought that was right.

From a bleed down perspective, that new meter should be an improvement. Remember, the capacitors will bleed down on their own. A 1 MΩ resistance would give about 0.1% bleed down in the first second. This calculator does not go to 10MΩ (http://hyperphysics.phy-astr.gsu.edu/hbase/electric/capdis.html ). Your greatest source of bleed down may be the capacitors themselves.

As for power, the device to which you linked requires a maximum of 5V DC. You will need to modify the LED power supply in the welder. That may be easily done. Do you have any pictures of the PCB for that supply? It may be simply a matter of changing the voltage regulator, assume that supply doesn't power other things.

I assume your OCV is on the order of 30V max or so. Be sure to set the meter to read a max of 200 V.

John

 

[lostintranslation]

yes, the bleed down will happen with the caps on their own, over time, but this is the display bleeding them faster than they would otherwise. I just need them to be as stable as possible for about 30 seconds or a minute, tops. The LED and the welder LM board are not on the same power supply circuit, are they? I can put them on their own circuits, it doesn't have to be a common ground. I thought that the CX102A and the CX102B were just options on common ground configuration or not?

here's the LM board I am using for the PCB of the welder(Edit: I know the wiring diagram says 50V, but I dropped back to 35V):
http://www.ebay.com/itm/LM2577-DC-D...161?pt=LH_DefaultDomain_0&hash=item485bc30a71

 

[lostintranslation]

i did find this, but they are "back ordered" so I may need to figure out how to make my own... if that's possible, or how to rig the CX102B up without this add on board.....?

http://www.circuitspecialists.com/cx-add-on-board.html

 

[jpanhalt]

It appears you are building a capacitor discharge welder. If so, how are you triggering the discharge?

Back to the issues at hand. Here is a snippet of the datasheet showing the need for a 5V supply to the LED voltmeter:



And in your schematic of the welder, you show a separate supply:



If it is a CD welder and you are trying to use the power supply or charging to drive the voltmeter, you will probably have problems. To see why, you will need to provide a more detailed schematic of your design.

John

 

[jpanhalt]

As for post #9, you lost me. Let's stick to what you have before buyingmore parts that may not be necessary.

John

Edit" Please confirm whether this is a CD welder.

 

[lostintranslation]

Thanks for all the insight, help and effort, I appreciate it immensely.

It appears you are building a capacitor discharge welder. If so, how are you triggering the discharge?

touching two alligator clip leads together that hold wires to be welded, or, if no weld will be made, there is a momentary delay normally off button that discharges the caps....

Back to the issues at hand. Here is a snippet of the datasheet showing the need for a 5V supply to the LED voltmeter:

View attachment 10633

And in your schematic of the welder, you show a separate supply:

View attachment 10634

If it is a CD welder and you are trying to use the power supply or charging to drive the voltmeter, you will probably have problems. To see why, you will need to provide a more detailed schematic of your design.

John
I tried to separate the power supply source for the LED initially so it was not drawing power from the welder circuit....

that wiring diagram is all I have and what I have to work from. Seeing the wiring helps me more than circuit diagrams and icons/symbols. If I can see it wired, it makes more sense to me. sorry, that's what I am working from.

 

[lostintranslation]

As for post #9, you lost me. Let's stick to what you have before buyingmore parts that may not be necessary.

John

Edit" Please confirm whether this is a CD welder.

it's an add on board that allows for the panel meter to read up to 200V... as it is, I believe it is only configured to read mV...?

sorry, thanks, just trying to find my way through this.

 

[jpanhalt]

The meter you have will read to 200V, if I understand its datasheet. Just set the DP. Did you not get the add-on board with the meter? If not, then you need it.

That still doesn't address your need for a 5-V supply, which you show in the diagram. You cannot omit it easily.

John

 

[lostintranslation]

The meter you have will read to 200V, if I understand its datasheet. Just set the DP. Did you not get the add-on board with the meter? If not, then you need it.

That still doesn't address your need for a 5-V supply, which you show in the diagram. You cannot omit it easily.

John

no, I did not get the add on board, at the time, I did not know I needed it, and the only place I can find it is not even the same place I bought the meter, and what's worse the only place I can find it, has it as back ordered, so i don't even know if I can get it.

what can I do to get the power supply correct for it, assuming I can manage to find the add on board I need? thanks in advance.

 

[lostintranslation]

is there any way I can wire the old volt meter and the new panel meter together to get the impedance I need from one, and volt metering I need from the other? I know, wild idea, but hey, I've had worse ideas. often, and repeatedly. just not lately. today. lol

 

[lostintranslation]

would I be better off ordering the CX 102 A with the 9 volt supply while I am getting the add on board rather than having to figure out how to get a 5 volt supply to the meter? I can return the CX 102 B....

 

[davenn]

The meter you have will read to 200V, if I understand its datasheet. Just set the DP. Did you not get the add-on board with the meter? If not, then you need it.................

John

No, the addon board is required for reading anything more than 200mV
The add-on board has a precision resistor divider network on it for being able to select 20V, 200V, 500V


Dave

 

[davenn]

would I be better off ordering the CX 102 A with the 9 volt supply while I am getting the add on board rather than having to figure out how to get a 5 volt supply to the meter? I can return the CX 102 B....

well it doesnt really matter 9V or 5V supply you need to sort out how to get either of those

AND SERIOUSLY you are going to have to make the effort to start drawing and using proper circuit diagrams
its extremely difficult for people to understand what you are doing and what mistakes you may have made in a construction
without being able to see the actual schematic of what you have built

You are really going to have to take the time to catch up with the rest of the world, else you are going to find your electronics
experience very difficult into the future

Dave

 

[jpanhalt]

I believe both meters need the add on board. It is possible to get the datasheet for the chip on that board and rewire it yourself. I did that, but I suspect that is not something you want to get into.

Have you tried your alligator-clip method of welding? I have concerns over that working. The CD welder I made, used a high-power SCR for firing. I also had abut 400,000 to 800,000 µF for my capacitors. The equivalent series resistance of the capacitors will limit your welding current.

Most important, 35V can be lethal. I know it is less than the 45 to 50 V usually considered lethal, but that threshold is highly variable. One can find case reports of welders being killed by lower OCV's. The cases I found were from China.

John