Electronics > Beginners
Hooking up 4 x 3v LED string lights to a 6v PSU
bob21:
And that seriously works for small wires? Wow. I thought it would have clamped in the jaws, glad you pointed that out :D
Just waiting to hear back from my friend to see if I can transfer money and use his prime. If it’s a no go (can’t see this being the case though) are there any high street alternatives? Or is this pretty much one of those price to functionality gems that no one else produces?
Edit: ok, scratch that. Got green light for amazon so Uni-T ordered, but also a neighbour who works for a telecoms company has lent me this: https://www.screwfix.com/p/kewtech-kt203-ac-dc-clamp-meter-400a/4048P?kpid=4048P&ds_kid=92700048793290430&ds_rl=1244066&gclid=Cj0KCQiApt_xBRDxARIsAAMUMu8DA0ohmKcjeAFfc-vQHwNb4LW314LOOg-5oqWlW5T9buupCpmoQWUaAnAnEALw_wcB&gclsrc=aw.ds that I can borrow until my Uni-T arrives. Is this suitable? It seems to mention DC current? Nevermind. It's completely lifeless... I guess that's why he didn't mind lending it to me ::) I'll wait for the Uni-T.
Brumby:
--- Quote from: bob21 on February 03, 2020, 08:20:08 am ---Nevermind. It's completely lifeless... I guess that's why he didn't mind lending it to me ::) I'll wait for the Uni-T.
--- End quote ---
Oh.
Seems it does do DC current via clamp so, yes, it will be able to measure DC current without having to cut into wires.
The lowest range, however, is 40.00A (the maximum value displayable on a particular range) - which means the resolution (last digit) is 10mA. This should be enough for you to get some idea of what's going on, but the Uni-T has a 1mA resolution on the lowest range which will provide more information.
Here's a trick: if you create several loops of wire, the current reading shown on the meter will be multiplied by the number of loops. Here is an example of 5 loops. The meter reading will be 5 times higher than the actual current flowing - because there are 5 wires carrying current through the clamp.
So to get the correct current in this example, you divide the displayed value by 5. Using the 30.00 A value displayed in this image, the actual current flowing through the wire would be 6.00 A.
Change the number of loops and you change the number you divide by.
bob21:
Makes sense. Thanks :) I am guessing using a mean calculation with more wraps like that is better for smaller wires?
I actually can't wait for this Uni-T to arrive now.... want to get stuck back in. :D
bob21:
I am just grabbing some other stuff for another project from CPC, and they have a ton of resistors. Is it worth me grabbing a small array for the toolbox? Maybe some of these:
https://cpc.farnell.com/search?st=22ohm%203w
https://cpc.farnell.com/search?st=22ohm%201w
https://cpc.farnell.com/search?st=10ohm%203w
https://cpc.farnell.com/search?st=10ohm%201w
I also want to connect the wires with plugs so it won't be a right faff to move the whole lot. I was thinking drill 3 holes in the ABS box, mount something like this: https://cpc.farnell.com/cliff-electronic-components/fm686803/circular-receptacle-pin-3-way/dp/CN16599?st=male%20female%20plug then have the corresponding plug on the PSU and lines. I can't seem to find these things sold in male and female sets, anyone know what they are called?
Zero999:
A kit of resistors is always a nice thing to have. At bare minimum I'd recommend an E12 kit of resistor values from 10R to 1M, preferably 0.5W metal film, but carbon film is fine for most applications.
Note, resistors come in standard values to make manufacture and specifying them easier. See the Wikipedia article.
https://en.wikipedia.org/wiki/E_series_of_preferred_numbers
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