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Topic: more than 5V? Help please (Read 661 times) previous topic - next topic


I want to use one Arduino pin to control 10 IR diodes.

The diode specs :
Forward Voltage (V) : 1.5~1.6
Forward Current (mA): 60mA Continuous, 120mA peak for 10% Pulse Width

How can i do that? How can i connect external power source to this pin so he can power up all this ir diodes?



Roy from ITCrowd: Have you tried turning it off an on again?
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Jan 28, 2013, 04:31 pm Last Edit: Jan 29, 2013, 09:44 am by dc42 Reason: 1
You have three options:

1. Connect the 10 LEDs in parallel, each with its own series resistor, and drive them from a supply of between 2.5V and 5V. See the link in JimboZA's post for this. If you want to drive the LEDs at 60mA each, your power supply will need to provide 600mA. The transistor also needs to carry 600mA, so the 2N3904 shown in that link is not suitable. I suggest BC337 or ZTX851. 2N2222A would probably be OK too, although not as good as the other two (i.e. higher voltage drop). A logic level mosfet would be best.

2. Connect the 10 LEDs in series, along with one series resistor, and use a power supply of about 24V. The power supply only needs to supply 60mA (or whatever current you want to run the LEDs at).

3. Use a combination of the above techniques, i.e. connect several strings in parallel, where each string contains a few LEDs in series and a resistor. For example, using a 5V supply, you could use 5 strings of 2 LEDs (total current 300mA). Or with a 12V supply you could use 2 strings of 5 LEDs (total current 120mA).
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Forward Current (mA): 60mA Continuous, 120mA peak for 10% Pulse Width

BTW, this doesn't mean you must run 60 mA continuous into the Leds, it's just stating what
level they can handle. For many apps, you actually don't need that much current. Visible Leds
rated at 20 mA current are often plenty bright with much lower currents. If you're building
an IR "flood lamp", then 60 mA is reasonable.

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