I’m using this copper tape to wire up doll house 12v halogen lights.
I’ve been pulling my hair out with continuity checks on the copper tape.
Sometimes you’d get a beep and 20 minutes later the beep was gone.
I was expecting the copper tape to act like cable, basically zero resistance. That turns out not to be the case because the sticky side, although conductive, has some inherit resistance.
Eventually I got so weirded out I switched my DMM to ohms and measure 39 ohms across a connection. The penny dropped and now I have a problem to solve.
After some more experiments I’ve learned that each piece of tape (40mm) adds 2 ohms.
So I can expect at least 50 ohms. Maybe 80 in some cases.
mmm Never used copper tape, but the resistance sounds very high. Are you sure there is not a coating on it or tarnished ? Copper exposed to the air will tarnish, which wont help, but it it stays shinny, then It could be coated with something to stop the air getting to the copper.
just to test, If you can. See if you can get solder to stick to each end, then measure it at via the solder.
A 12V battery.
I am not trying to be funny here but you have to think about it a bit. You could calculate the resistor value to get 12V at the lamp but you would probably find that 15V is OK. Depends a bit on the lamp. You are in charge of that bit..
No you can’t. You will drop 12V across the zener diode which only leaves 3V to be shared between the resistor and lamp.
I thought you would have played around with circuits enough by now to know that this lamp circuit is nothing like the 3.3V circuit you presented above.
Copper tape is usually OK. You will find that if it is a bit old you will have to press the meter probe points a bit harder to force them through any tarnish or oxidation that might be present.
Probably normal. I am not sure but maybe the sticky is not too conductive. I have usually done what most do and soldered any connections. Clean the tape then lightly tin the connecting surfaces. Press the surfaces together with a good soldering iron and when hot enough apply a little solder around the edges until it wicks between the tapes in the connection area. You will need a larger iron tip for this. I have an 80W iron I use for this sort of thing. makes the job a lot quicker and cleaner.
If you need 12V at the lamp and you have a 12V supply what the hell is the 50Ω resistor for. That is always going to provide a lower voltage.
That is a high resistance for 40mm of tape. Don’t believe it. How wide and thick is this tape. Must be almost fine foil. Solution if this measurement is correct, use a thicker tape.
Cheers Bob
In that circuit, the 50 ohms is a stand in for the copper tape. This circuit shows what I currently have, with only 6v at the lamp.
This is the problem I need to solve.
My ability to make mistakes has no equal
Yep I see now what I didn’t understand.
The 12v zener diode guarantees the voltage ACROSS it to be 12v.
So yes, I understand that that leaves 3v in the upper portion.
So, now I understand why I have to do this.
Hi pix
You can’t hope to have anything under control while surrounded with uncertainties. In this case tour uncertainties seem to be this tape you are using.
By the way you have not replied to the query on exactly what this tape is and size. It sounds more like resistance wire than copper tape.
My tip here is ignore everything else until you have fixed this tape. You need to get rid of these unknown and unreliable quantities and take control of what is going on. In other words don’t let this tape or whatever it is dictate to YOU what is going to happen. YOU take control. You cannot depend on the VERY UNCERTAIN resistance of your tape installation to be a voltage dropper or anything else. You have to get this down to near zero to take control of your voltages and currents.
You will have to excuse my French but what you have described above seems to me to be just so much crap. There is something radically wrong here and you just have to find what it is.
Cheers Bob
If you are using the Core product SKU: PRT-10561 the headline says non conductive adhesive so it needs to be cleaned and soldered.
Don’t worry Bob I’m not saying I’m going to ignore the problem.
I’ve got some other tasks that need doing, then I’ll return to the tape and maybe a fresh mind will yield some new ideas or experiments.
It’s not like I’m working with zero empirical data here. The problem circuit in the doll house, the one I was trying to get continuity on, measures 38 ohms. That’s a known quantity.
Some other circuits are as low as 12 ohms and the longest run with the most connections is 49.4 (which is where that 50 ohm number is from).
I know that I want to throw 12v into the system and then measure the voltage at the light and common ground. That would confirm my measurements. I’ll get around to that.
I will also contact the manufacture to get clarity on the exact tolerances of the lights. That way I know what I’m aiming for exactly.
Good advice, and to be fair, I always do. I just do it slower, possibly because I’m young and clumsy.
To be honest I would expect maybe 1Ω or 2Ω at most. Probably less.
Experiment: get 2 bits of tape and join. compare a non soldered join (which I think is what you have) then a soldered join. You might see a difference. Measure a known length of tape. make sure you meter probes penetrate any coating or oxidation present. Let us know the result.
Cheers Bob
The conductive adhesive on the tape does work, but it’s not perfect. I assumed that adding layers to my tape would increase the conductivity, but that doesn’t seem to be the case. Adding two pieces of tape side by side with and joining them was the ticket because now the adhesive has a greater surface area to play with. I got one strip down from 58 ohms to 5 just by adding more surface area to each connection.
I might still explore ways to ensure 12v, but it’s probably not required now. 11.5v is still quite workable.
Hi Pix
Doesn’t matter how well you do it depending the “conductive” stick bit for a connection is a bit hairy at best I think. Personally I would solder the joins for repeatability at least.
You don’t have to try and solder the sticky bits. Just fold double the end of one piece with sticky side inwards then solder the resultant copper surfaces together.
Like this
Unfortunately the reason I chose conductive adhesive tape in the first place is because there isn’t enough room in the doll house to safety use a soldering iron (at least not my iron). The joint is all the way on the back wall so with two hands in there you can’t see what your doing. I don’t have a steady hand as it is so I’ll burn myself for sure.
I think I’ll just live with 5-10 ohms. It’s not the end of the world.
