HI all.
I would like some help with a circuit please. I have discalcula so please bare with me.
I have made an array of 120 5mm U.V Led's for an exposure tank. I have divided the Led's into groups of 4 and have a 47ohm resistor before each group. I am taking power from the emitter of a Tip120. The Tip120 is being switched on by a LDR. The LDR is controlled by a 555 monostable timer circuit.
The TIP120 gets hot. I have tried to compensate for this by adding a large heatsink.
My question is is the TIP120 able to drive this many LED's? the forward current on each LED is 20ma. I can't quite get the numbers to make sense to be able to calculate what's required. I did think I could just divide the array into to two with two TIP120's, but then thought I could probably put the TIP120's in series to compensate.
Anyhow. Am a bit out of my depth here so looking for advice.
Best
Darren
I would like some help with a circuit please. I have discalcula so please bare with me.
I have made an array of 120 5mm U.V Led's for an exposure tank. I have divided the Led's into groups of 4 and have a 47ohm resistor before each group. I am taking power from the emitter of a Tip120. The Tip120 is being switched on by a LDR. The LDR is controlled by a 555 monostable timer circuit.
The TIP120 gets hot. I have tried to compensate for this by adding a large heatsink.
My question is is the TIP120 able to drive this many LED's? the forward current on each LED is 20ma. I can't quite get the numbers to make sense to be able to calculate what's required. I did think I could just divide the array into to two with two TIP120's, but then thought I could probably put the TIP120's in series to compensate.
Anyhow. Am a bit out of my depth here so looking for advice.
Best
Darren