Guide's for a DIY LED strip for a 25cm tank

[oreo54]

Wait so whats the difference? I put LED driver into ebay search and those are the stuff I'm getting?

You know those reels you can buy of LEDs? They run off either a 12V or 24V constant voltage power supply.
Current of said power supply is dictated by how long the string is..

Constant Voltage vs. Constant Current Drivers — 1000Bulbs Blog

Learn the difference between a constant current LED driver and constant voltage LED driver in order to avoid using the wrong power source for your lighting.

blog.1000bulbs.com

This is what a sort of correct constant current driver looks like.
current listed
Voltage range listed
dimming listed
Wouldn't recommend 1050mA though. Stick to around 500mA
@ 36V maximum output you would have available an average of 4V per diode..

Remember you need to ADD up all the voltages of your series LEDs to calculate what you need in a driver.
Technically you would need the exact real voltage of each at the current you want too drive them at but few go this far into detail. Needs to be figured using the real diode string for the most part..

 

[PeterLL]

You know those reels you can buy of LEDs? They run off either a 12V or 24V constant voltage power supply.
Current of said power supply is dictated by how long the string is..

Constant Voltage vs. Constant Current Drivers — 1000Bulbs Blog

Learn the difference between a constant current LED driver and constant voltage LED driver in order to avoid using the wrong power source for your lighting.

blog.1000bulbs.com

This is what a sort of correct constant current driver looks like.
current listed
Voltage range listed
dimming listed
Wouldn't recommend 1050mA though. Stick to around 500mA
@ 36V maximum output you would have available an average of 4V per diode..

Remember you need to ADD up all the voltages of your series LEDs to calculate what you need in a driver.
Technically you would need the exact real voltage of each at the current you want too drive them at but few go this far into detail. Needs to be figured using the real diode string for the most part..

Thank you thank you think im getting it... slowly.
So would this one work for example: https://www.ukled.co.uk/eaglerise-constant-current-led-driver-350-700ma+led_output_current_cc-500mA

The 500mA one, with a maximum of 35V output, any reason that should work then? It has a 12W output but does the power matter then?

 

[oreo54]

Thank you thank you think im getting it... slowly.
So would this one work for example: https://www.ukled.co.uk/eaglerise-constant-current-led-driver-350-700ma+led_output_current_cc-500mA

The 500mA one, with a maximum of 35V output, any reason that should work then? It has a 12W output but does the power matter then?

Well first that driver is dimmable only by a wall dimmer (triac dimming) but fine IF that is what you want. I woudn't recommend it and max watts look low.
Second, watts are only a guideline to maximum output available.. So in a sense yes w/ a constant current driver watts don't matter except for the top end..

Take your string and assume 3.6V per diode.
3.6 x 9 = 32.4 volts..
If you get a driver w/ a range of 24-36V and a current set point of 500mA your watts out are 16.2. (32.4 x .5)
Same driver except current set point is 1A = 32.4 x 1 = 32.4 Watts (actually this number (sum of voltages, see chart below) will increase slightly but lets not get too complicated atm)

Point sort of is you need to ignore watts but not..

Watts = Volts X amps about the only equation important here.
Next would be the diodes current draw increases with voltage applied.

Last thing would be that a diodes efficiency ( photons/watts ) decreases as current rises but heating increases.

 

[PeterLL]

Well first that driver is dimmable only by a wall dimmer (triac dimming) but fine IF that is what you want. I woudn't recommend it and max watts look low.
Second, watts are only a guideline to maximum output available.. So in a sense yes w/ a constant current driver watts don't matter except for the top end..

Take your string and assume 3.6V per diode.
3.6 x 9 = 32.4 volts..
If you get a driver w/ a range of 24-36V and a current set point of 500mA your watts out are 16.2. (32.4 x .5)
Same driver except current set point is 1A = 32.4 x 1 = 32.4 Watts (actually this number will increase slightly but lets not get too complicated atm)

Point sort of is you need to ignore watts but not..

Watts = Volts X amps about the only equation important here.

Sooo I don't mind too much about a dimming feature, but what other options would you recommend then? Im looking at dimmable ones and its starting to occur Im not gonna find one with a wee slider so how else do they dim?
Okay so the 500ma driver is good, the range of watts is good, but the power output was wrong as it was too low at 12... So how about this one? https://www.ukled.co.uk/mean-well-p...ly-25w-350-1050ma+led_output_current_cc-500mA

 

[oreo54]

Sooo I don't mind too much about a dimming feature, but what other options would you recommend then? Im looking at dimmable ones and its starting to occur Im not gonna find one with a wee slider so how else do they dim?
Okay so the 500ma driver is good, the range of watts is good, but the power output was wrong as it was too low at 12... So how about this one? https://www.ukled.co.uk/mean-well-p...ly-25w-350-1050ma+led_output_current_cc-500mA

OK, had to et to the spec sheet..sorry that site is a bit annoying but anyways here goes:

PLM-25-MEAN WELL Switching Power Supply Manufacturer

MEAN WELL is one of the world's few standard power supply mainly professional manufacturers, covering 0.5 to 25,600W products are widely used in industrial control, medical and other fields, in line with international safety certification, short delivery of spot inventory.

www.meanwell.com

"E" is 250V AC only.. so OK for you.
500 is 500mA w/ a voltage range of 30-50V..
30/9 = 3.33v average for your leds. May be cutting it close on the low end. If you are using low voltage LEDS (reds) you may not reach enough voltage on adding up the diode voltages.
700 is 21-36V range..
36 = 4v per led.. so as long as you aren't using too many high voltage type diodes (purple/UV) should be fine.
IF by some chance your string voltage exceeds 36v it will just run at a lower current than the set point.

Non-dimmable driver..

hmm, I'd probably go w/ the 500mA you should clear the 30v lower limit.
If not just add a diode.

The diodes you bought had specs.. add the voltages up from that. Also what was the current at that voltage?

 

[oreo54]

Oh as to dimming LED's can be dimmed using the following methods depending on the specific driveer.
Most common ones:
Triac dimming
Potentiometer dimming
10V analog
10V PWM
5V PWM

some drivers will do multiple types.
Back later btw..

 

[PeterLL]

Sorry it was getting to 4am here so had to go to bed lol,
Okay so its mostly White / Purples so the 500mA one should work. What does the current affect on the LED? Like what is the benefit of a 700mA to a 500mA?
Not sure what you mean by adding up the current at the voltage?
Cheers Ill look into the types of dimming you just mentioned

 

[oreo54]

Sorry it was getting to 4am here so had to go to bed lol,
Okay so its mostly White / Purples so the 500mA one should work. What does the current affect on the LED? Like what is the benefit of a 700mA to a 500mA?
Not sure what you mean by adding up the current at the voltage?
Cheers Ill look into the types of dimming you just mentioned

If you apply 3Vs across the below representative diode it will draw like 340mA
If you have a constant current driver of say 500mA the voltage across the diode will be like 3.05V
If you set the current to 1000mA the voltage will be like 3.27v.
10 diodes in series will need 30.5V @ 500mA,
10 diodes in series @ 1000mA will need 32.7V
So when picking a driver one would like to know the real voltage at a set current that you want to use.

The current determines the brightness and sadly the amount of heat you run the diode at.
Trade-off is:
More current more gross photons more heat you need to dissipate.
Less current less heat less photons but on a p/watt basis you gain.
Like if you get 1000 photons (really low number btw) out at 1000mA one would expect 500 photons (1/2 current, 1/2 output) out at 500mA
Doesn't quite work that way, more like 600 photons.
doubling the current one would expect 1200 photons as well not 1000.

 

[PeterLL]

Thank you think I am actually starting to understand the physics behind this now... maybe slightly lol.
Well I got the LED working!!! For about 5 minutes and then the LED's are now incredibly dim, and 2 (the 2x Bright Blues) are not lit at all. What do you think this could be?

 

[PeterLL]

The fact all but the blues are lit but incredibly dim makes me think the circuit is still complete so I'm not sure whats wrong.
Any ideas @oreo5457

 

[oreo54]

The fact all but the blues are lit but incredibly dim makes me think the circuit is still complete so I'm not sure whats wrong.
Any ideas @oreo5457

Sounds like the voltage is too low.. or the driver went into fail safe though usually in my experience they sort of blink.
do you have a VOM? Volt /ohm meter?
Sometimes too low in current does the same..
Also as mentioned make sure no solder is conducting to the aluminum heat sink.

 

[PeterLL]

Sounds like the voltage is too low.. or the driver went into fail safe though usually in my experience they sort of blink.
do you have a VOM? Volt /ohm meter?
Sometimes too low in current does the same..
Also as mentioned make sure no solder is conducting to the aluminum heat sink.

Thank you,
My mistake, all the LEDs are lit up just dim like this:

they were FULLY operational for a good few minutes.
what would cause the voltage to be low, or for the driver to go into failsafe?How would I fix that?
And no I still do not have a VOM I’ve been meaning to get one.
There’s no solder touching the aluminium I’ve made sure.
Cheers

 

[oreo54]

If they were working but now dim I'd check my solder joints.. May be a cold one that got weaker.
Btw solder or wire only need to touch the edge of the star..
Only reason I mention this is even the best can get this.

I'm still going w/ a current/voltage leak somewhere. Takes little voltage to light the diodes really, regardless of charts..

 

[PeterLL]

If they were working but now dim I'd check my solder joints.. May be a cold one that got weaker.
Btw solder or wire only need to touch the edge of the star..
Only reason I mention this is even the best can get this.

I'm still going w/ a current/voltage leak somewhere. Takes little voltage to light the diodes really, regardless of charts..

Will give all the solder joints a once over with the solder then. What do you mean by the touching edge of the star? For a leak or for passing current through the series?

 

[oreo54]

Will give all the solder joints a once over with the solder then. What do you mean by the touching edge of the star? For a leak or for passing current through the series?

For a leak. Once last the top black layer it's all conductive to the aluminum. Your getting enough current/ voltage to light most somewhat.
Using ribbon led's an analogy would be w not enough voltage/current getting to the end due to resistance increases with distance. So they light unevenly.

Also your driver will drop voltage to meet the current set point. If current draw increases due to a tiny " leak" to ground it will drop the voltage across the string to compensate.

A vom is really a necessity
Depending on the min voltage of your driver you could troubleshoot by taking one end off the string and just jumper to a few at a time..in series till they go dim.
Driver needs a low end limit of about 6 volts. 2-3 would be ideal.
No guarantee but you normally can't make fatal mistakes. You know accidentally reversing or dead shorting because most drivers/ power supplies have short protection and not enough voltage to break down the diodes in reverse bias mode BUT no guarantee.
Asking as you know plus and minus no problems doing it right.

 

[PeterLL]

For a leak. Once last the top black layer it's all conductive to the aluminum. Your getting enough current/ voltage to light most somewhat.
Using ribbon led's an analogy would be w not enough voltage/current getting to the end due to resistance increases with distance. So they light unevenly.

Also your driver will drop voltage to meet the current set point. If current draw increases due to a tiny " leak" to ground it will drop the voltage across the string to compensate.

A vom is really a necessity
Depending on the min voltage of your driver you could troubleshoot by taking one end off the string and just jumper to a few at a time..in series till they go dim.
Driver needs a low end limit of about 6 volts. 2-3 would be ideal.
No guarantee but you normally can't make fatal mistakes. You know accidentally reversing or dead shorting because most drivers/ power supplies have short protection and not enough voltage to break down the diodes in reverse bias mode BUT no guarantee.
Asking as you know plus and minus no problems doing it right.

So sorry for not replying. I did get it all operational now thanks to your help. Really appreciate the time youve taken out to help me with all this over this whole thread, so thank you! Have helped me get to grips with the physics behind this and hopefully I can try pass on some of the knowledge.