Hello, Thanks for taking the time to read my question. I'm a complete newbie and while I have read a lot of forum posts trying to research the answers, I clearly have basic gaps in my understanding and have just come away more confused than when I started.
I've been asked to help build a basic LED lighting circuits after somebody left a project, but I'm worried the original project assumptions are incorrect but I'm also significantly out of my comfort zone so can't be confidant in my assessment or understanding.
The project is to create a simple set of 160 LED lights in totally broken up across 4 parallel lines. Some of the hardware has already been purchased
LED's are RS (7133955) Nichia 500D White LED 5mm (T-13/4)
The datasheet states:
Max Forward Current is 30ma
Reverse Voltage is 5v
Forward Voltage is 3.2V at 20ma with range of Min 2.65V to 3.5V
RS Resistors 10 Ohms +-5% (Brown, Black, Black, Gold)
Power supply is assumed to be 5 volts but hasn't actually be purchased but no current calculations can be found. Is 5v enough given voltage drop?
We have made 4 lighting rigs consisting of 2 cables with 40 LEDs in parallel down the length (10 meters roughly) of the cable with each LED connected to a 10 Ohms resistor. I can't find any documentation from the original lead as to why a 10 Ohm resistor was chosen. I understand that having a resistor will help the LEDs be the same brightness. Which I believe is one of the most common issue when wired in parallel (assuming I've understood correctly). What I'm worried about is how the value of 10 Ohms was calculated. The original plan was to connect each one of the lighting rigs to a shared power supply but again no details of what that power supply was going to be can be found. So, I need to establish the power supply requirements in terms of 5v, 12v or 24v
Guess the first question is this the best way to achieve a total of 160 LEDs? or would it be better to do a parallel series of lights? The originally person has made many rigs already. So if its possible to do this in standard parallel configuration safely I'd like to avoid recreating all their work. Assuming the 10 Ohm resistors it actually correct.
I think this is a correct representation although, it would be times 4 rigs that would connect to the power supply.
To establish what power supply needs I have. I've used information from https://www.petervis.com/electronics/led/led-resistor-calculator.html
"The total current is the sum of all the individual forward currents of each LED."
So assuming you use the Max Forward Current rather than the typical 20ma operating current.
Max Forward Current 30ma x 40 = 1.2a
Then as we've got 4 of these rigs 1.2. * 4 = 4.8a is that right?
Looking at the same page I can’t find any combination of input voltage that would get me to a 10 Ohms resistor. So, I'm even more lost now.
5V @ 3.2 VF = 90 ohms.
12v @ 3.2 VF = 440 Ohms.
I'm sorry this questions / post is probably all over the place and I'm sure I'm showing my huge naivety in general. So, I really do welcome all feedback and I thank you in advance for any help you can give me.
I've been asked to help build a basic LED lighting circuits after somebody left a project, but I'm worried the original project assumptions are incorrect but I'm also significantly out of my comfort zone so can't be confidant in my assessment or understanding.
The project is to create a simple set of 160 LED lights in totally broken up across 4 parallel lines. Some of the hardware has already been purchased
LED's are RS (7133955) Nichia 500D White LED 5mm (T-13/4)
The datasheet states:
Max Forward Current is 30ma
Reverse Voltage is 5v
Forward Voltage is 3.2V at 20ma with range of Min 2.65V to 3.5V
RS Resistors 10 Ohms +-5% (Brown, Black, Black, Gold)
Power supply is assumed to be 5 volts but hasn't actually be purchased but no current calculations can be found. Is 5v enough given voltage drop?
We have made 4 lighting rigs consisting of 2 cables with 40 LEDs in parallel down the length (10 meters roughly) of the cable with each LED connected to a 10 Ohms resistor. I can't find any documentation from the original lead as to why a 10 Ohm resistor was chosen. I understand that having a resistor will help the LEDs be the same brightness. Which I believe is one of the most common issue when wired in parallel (assuming I've understood correctly). What I'm worried about is how the value of 10 Ohms was calculated. The original plan was to connect each one of the lighting rigs to a shared power supply but again no details of what that power supply was going to be can be found. So, I need to establish the power supply requirements in terms of 5v, 12v or 24v
Guess the first question is this the best way to achieve a total of 160 LEDs? or would it be better to do a parallel series of lights? The originally person has made many rigs already. So if its possible to do this in standard parallel configuration safely I'd like to avoid recreating all their work. Assuming the 10 Ohm resistors it actually correct.
I think this is a correct representation although, it would be times 4 rigs that would connect to the power supply.
To establish what power supply needs I have. I've used information from https://www.petervis.com/electronics/led/led-resistor-calculator.html
"The total current is the sum of all the individual forward currents of each LED."
So assuming you use the Max Forward Current rather than the typical 20ma operating current.
Max Forward Current 30ma x 40 = 1.2a
Then as we've got 4 of these rigs 1.2. * 4 = 4.8a is that right?
Looking at the same page I can’t find any combination of input voltage that would get me to a 10 Ohms resistor. So, I'm even more lost now.
5V @ 3.2 VF = 90 ohms.
12v @ 3.2 VF = 440 Ohms.
I'm sorry this questions / post is probably all over the place and I'm sure I'm showing my huge naivety in general. So, I really do welcome all feedback and I thank you in advance for any help you can give me.