Syncrolight Snowman

[jagnew]

I’ve just built 2 of the Syncrolight animated snowmen and now need to mount the led strings. How many led’s are classed as a short run and what resistor value do I need to fit to these short strings? I’m using a 24v 5a supply and using strings from Syncrolight. Thanks

[sandy123]

Hi
Whatever you do, DON'T use the 24v 5Amp transformer (don't know if they are still selling them!) on that animation. Output voltage will be in excess of 31-32volts. That will burn out your LEDs. It's what is classified as an 'unregulated' supply and will only come down to around 24v output when you have it loaded to about 4Amps
If you are using a regulated supply like the one advertised on the Syncrolight website for around £37 (I think!), then there's no issue and you don't need to worry about adding Resistors to the circuit. These supplies kick out 24v.
Resistors are used to limit current flow, and/or 'drop' voltage in a circuit.
Hope that helps
Regards
Sandy

[jagnew]

Thanks Sandy, I should be ok then because it was the Light show starter pack I bought already wired and with 24v power brick already wired. I do have 4 other DC08A’s that I will be powering with other 24v 5a regulated supplies as I build my system but need to do more research on resistors and values.

It was as I was reading the build instructions I noticed it mentioned using a resistor on the short runs….some of which are only 9 LED’s

[sandy123]

Unfortunately, I can't really help you there. '9 LEDs' has thrown me a bit.
I know they do 18, 24 & 36 LED strings. If memory serves me correctly - these don't (or didn't) branch out in sets of 9 (i.e. could be cut every 9 LEDs where there's only two wires. I have 'reversed engineered some of these strings in the past, and found that they were 'configured' (wired) similar to a ladder (i.e. a series/parallel configuration). The 'ladder' stiles were the positive and ground wires - and the 'rungs' consisted of 6 to 8 LEDs wired in series ans each 'rung' had a resistor fitted to that part of the series. If the strings that you have, allow them to be cut every 9 LEDs, then there should already be a resistor in the circuit (it will be soldered directly to one of the LEDs and enclosed in the heatshrink that encapsulates it.
If the build instructions don't specify any value of resistor, I can only advise that you contact the support desk at Syncrolight and as them for advice on that.
As for Resistors - OHMS Law basically states that V=IxR (Voltage = Current (amps) x Resistance
Example:- 24v DC supply across 7 white LEDs in series
White LEDs nominally drop approx 3v each, so 7x3 = 21Volts
You need to use a resistor to drop the other 3 Volts!
required current say, 10mA (which will flow through all 7 LEDs to light them all)
OHMS Law - 3v/.01A = 300 ohms (that's the size of resistor you require)
BUT!!! you also need to work out the wattage, so you don't burn out the resistor
W = IxIxR = .01 x.01 x 300 = 0.03Watts (so a small standard 300ohm resistor rated at 1/8th Watt is what you would use)
Hope that gives you some insight
Regards
Sandy

[jagnew]

(29-01-2022, 09:39 PM)sandy123 Wrote: Unfortunately, I can't really help you there. '9 LEDs' has thrown me a bit.
I know they do 18, 24 & 36 LED strings. If memory serves me correctly - these don't (or didn't) branch out in sets of 9 (i.e. could be cut every 9 LEDs where there's only two wires. I have 'reversed engineered some of these strings in the past, and found that they were 'configured' (wired) similar to a ladder (i.e. a series/parallel configuration). The 'ladder' stiles were the positive and ground wires - and the 'rungs' consisted of 6 to 8 LEDs wired in series ans each 'rung' had a resistor fitted to that part of the series. If the strings that you have, allow them to be cut every 9 LEDs, then there should already be a resistor in the circuit (it will be soldered directly to one of the LEDs and enclosed in the heatshrink that encapsulates it.
If the build instructions don't specify any value of resistor, I can only advise that you contact the support desk at Syncrolight and as them for advice on that.
As for Resistors - OHMS Law basically states that V=IxR (Voltage = Current (amps) x Resistance
Example:- 24v DC supply across 7 white LEDs in series
               White LEDs nominally drop approx 3v each, so 7x3 = 21Volts
               You need to use a resistor to drop the other 3 Volts!
                required current say, 10mA (which will flow through all 7 LEDs to light them all)
               OHMS Law -     3v/.01A = 300 ohms  (that's the size of resistor you require)
               BUT!!! you also need to work out the wattage, so you don't burn out the resistor
               W = IxIxR   = .01 x.01 x 300 = 0.03Watts (so a small standard 300ohm resistor rated at 1/8th Watt is what you would use)
Hope that gives you some insight
Regards
Sandy

Yes these are just the 200 led strings so I know to cut at the twin wire so expect to need to hide some unused LED’s behind the prop. Thanks for the in-depth look at resistors, gives me lots of info. I was hoping Craig would answer the thread. It would have been great to have more info in the instructions about resistor values but gives me more stuff to learn in the next 11 months ;-)

[Craig]

Hi

The current animation packs all come with a regulated power supply and therfore no additional resistors are required for short led strings.

In the past led our strings were designed for the higher voltage of unregulated power supplies and hence an extra resistor was required to protect shorter strings of leds.

Note there is also brightness limit setting on the DC08s that can be used to help reduce the effective voltage exposed to the leds. This is mainly for unregulated power supplies but there is no harm in setting this to the lowest value that gives an acceptable brightness.

Also yes it's often necessary to hide a few leds behind as you can not always cut to the exact number of leds required.Adding a little black tape over the led will stop any light bleeding around the edges.


Craig

[jagnew]

Thanks Craig that’s good news. I was planning on starting at a lower brightness to start anyway.