Electronics > Beginners
Hooking up 4 x 3v LED string lights to a 6v PSU
Brumby:
--- Quote from: Zero999 on February 03, 2020, 01:00:28 pm ---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.
--- End quote ---
+1 for this.
You will end up using just a few values from this on a regular basis (that you will end up getting more of those values), a few more every now and then and most will be sitting there 10 years from now. BUT - it's always worth having a range on hand if you are going to be experimenting and for the price they go for, it's a no-brainer.
bob21:
Thanks both. Do you mean something like this? https://cpc.farnell.com/unbranded/mf0w2ffe012kil/resistor-kit-0-5w-1-e12/dp/RE03416
It's quite a lot to drop on a starter project though.
Also, @Zero999 is "Through-hole Resistor with metal oxide film element and high safety standard high purity ceramic core." what you mean by metal film?
Ok, for like a third of the price of that kit, I can get these:
--- Code: ---MCKNP03WJ0100AA9 MULTICOMP PRO MULTICOMP PRO Resistor, Wirewound, 10R, 5%, 3W
MOR01SJ0100A10 MULTICOMP PRO MULTICOMP PRO Resistor, 1W 5% 10R
MOR03SJ0220A19 MULTICOMP PRO MULTICOMP PRO Resistor, 3W 5% 22R
MF50 10R MULTICOMP PRO MULTICOMP PRO Resistor, 0.5W 1% 10R, 50 Pack
MF50 12R MULTICOMP PRO MULTICOMP PRO Resistor, 0.5W 1% 12R, 50 Pack
MF50 15R MULTICOMP PRO MULTICOMP PRO Resistor, 0.5W 1% 15R, 50 Pack
MF50 18R MULTICOMP PRO MULTICOMP PRO Resistor, 0.5W 1% 18R, 50 Pack
MF50 22R MULTICOMP PRO MULTICOMP PRO Resistor, 0.5W 1% 22R, 50 Pack
MF50 27R MULTICOMP PRO MULTICOMP PRO Resistor, 0.5W 1% 27R, 50 Pack
MF50 33R MULTICOMP PRO MULTICOMP PRO Resistor, 0.5W 1% 33R, 50 Pack
MF50 39R MULTICOMP PRO MULTICOMP PRO Resistor, 0.5W 1% 39R, 50 Pack
MF50 56R MULTICOMP PRO MULTICOMP PRO Resistor, 0.5W 1% 56R, 50 Pack
MF50 68R MULTICOMP PRO MULTICOMP PRO Resistor, 0.5W 1% 68R, 50 Pack
MF50 82R MULTICOMP PRO MULTICOMP PRO Resistor, 0.5W 1% 82R, 50 Pack
MF50 100R MULTICOMP PRO MULTICOMP PRO Resistor, 0.5W 1% 100R, 50 Pack
MFP1-12R JI TT ELECTRONICS / WELWYN TT ELECTRONICS / WELWYN Resistor, 1W 5% 12R
MOR01SJ0150A10 MULTICOMP PRO MULTICOMP PRO Resistor, 1W 5% 15R
MFP1-18R JI TT ELECTRONICS / WELWYN TT ELECTRONICS / WELWYN Resistor, 1W 5% 18R
MOR01SJ0220A10 MULTICOMP PRO MULTICOMP PRO Resistor, 1W 5% 22R
MCKNP01WJ033KA10 MULTICOMP PRO MULTICOMP PRO Resistor, Wirewound, 0R33, 5%, 1W
MFP1-39R JI TT ELECTRONICS / WELWYN TT ELECTRONICS / WELWYN Resistor, 1W 5% 39R
MFP1-56R JI TT ELECTRONICS / WELWYN TT ELECTRONICS / WELWYN Resistor, 1W 5% 56R
MOR01SJ0680A10 MULTICOMP PRO MULTICOMP PRO Resistor, 1W 5% 68R
MFP1-82R JI TT ELECTRONICS / WELWYN TT ELECTRONICS / WELWYN Resistor, 1W 5% 82R
MOR01SJ0101A10 MULTICOMP PRO MULTICOMP PRO Resistor, 1W 5% 100R
--- End code ---
I've gone for 1% variance and MOR where I can.
Just gotta find those plugs now ;) Looks like eBay wins for that: 223071120027
Zero999:
Yes, that looks suitable. Repeat that pattern up to 1M and you'll have a nice stock.
I personally have E24 from 10R to 1M and E12 from 1R to 10R and 1M to 10M, but it's a bit overkill for the hobbyist.
bob21:
It's here! :-DMM
I switched to '2A~' and with the entire circuit hooked up I get:
1 wire: ~0.158
5 wraps: ~0.820
This is measured from 1 of the wires of the PSU using the clamp, before the series/parallels start (at the purple dot).
I did notice when doing the single wire, it was quite an exact immediate number. With 5 wraps it took a while to climb and stabilise.
More to follow. Doing this around making dinner etc.
Edit:
Ok, got it:
Line 1 (10 small globes)
Single wire: 41mA
5 Wraps: 198mA
Line 2 (10 Large Globes)
Single wire: 36mA
5 Wraps: 256mA
Line 3 (6 White Stars)
Single wire: 37mA
4 Wraps: 146mA (could only manage 4 wraps as wire very short before 1st star)
Line 4 (15 Globes)
Single: 41mA
5 Wraps: 245mA
Lines 2 and 4 seem a bit off when dividing the wrap figure (it doesn't give exactly the single wire figure). Whereas 1 and 3 are almost spot on. Is this normal?
I suppose the important thing to note is that the total figures are adding up for the single wires:
Sum of singles: 155mA, and is 158mA measured from PSU wire.
But I have probably screwed up my wrapping a bit:
Sum of wraps: 881mA (obviously taking into account that line 3 needs to be 182mA for this calc), and is 820mA from PSU wire
Do I need to retest?
Also, I noticed that the draw from 1+2 (41+36) is almost the same as 3+4 (37+41)... so circuit A is pulling 77mA and circuit B is pulling 78mA..... does this mean they are [kind of] correctly balanced?
Edit2: Btw, an extra thanks to Brumby for the DMM recommendation. This thing is great. It's about 1/3rd the size of the old piece of junk I had it's auto ranging is something I didn't have before along with a zero and hold button etc which is awesome and it's super intuitive to use.
Edit3: Just got to pop out, when I get back I'll see if I can work out what resistors I need for each circuit.
gf:
--- Quote from: bob21 on February 04, 2020, 05:47:25 pm ---This is measured from 1 of the wires of the PSU using the clamp, before the series/parallels start (at the purple dot).
[...]
--- End quote ---
Which current limiting resistor values did you use for each these measurements?
What do you mean with "5 Wraps"? Do you mean 5 lines (of the particular lamp type) connected in parallel?
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