Making an infrared(IR) lighting for Raspberry Pi NOIR Camera and making an enclosure before installing RPI camera – Part 4 of 4 : Combining software and hardware…….still in progress, est. completion date Dec 2020.

Making an IR lighting for Raspberry Pi(RaspPi) NOIR (no infrared filter) camera. This IR will assist the camera to see better in the dark. Below is the circuit diagram for the prototype.

the night vision for Raspi cam when nightfall🧐
In bright surrounding, the LDR causes the transistor to off.
Now the LDR is covered to simulate dark surrounding, this cause transistor to ON. Indicator and IR LEDs lighted up. 👍

In theory each IR LED draws 20mA, indicator LED draws 20mA. Estimated, I need 30 IR LEDs. The below prototype uses 2 NPN transistors (2N2222), arranged to Darlington pair combination. Darlington pair give the current gain as hfe = hfe1 * hfe2 .

Current at the base, DMM scale is 20mA. So this reading is 0.02mA = 0.00002A = 20uA
Current reading at the emitter, DMM scale is 10A, so reading is 0.38A.

Base on the 2 pics above, we can calculate the hfe. hfe = 0.38/0.00002 = 19000 times. This is Darlington pair combination. So taking square root, 190000.5 = 137.84 times.

Hence without the power of Darlington pair the current gain in 137.84 times.

The below video points out that the NPN transistor 2n2222 is not suitable to switch and transport current to the LEDs as it gets pretty hot , imo using a relay together with transistor is better.

Just bought a Darlington pair NPN power transistor, TIP120. Instead of using a relay with transistor, I have decided to try using this power transistor which have a rating of 60V, 5A. According to TIP120 datasheet, the VBE is 2.5v(max.). So I think should be ok.

TIP 120 NPN power transistor, packed with the power and goodness of Darlington pair, all in 1 package. 🤙
Max. Collector current is 5A, so we are within range, at 0.68A when dark.

Using Eagle PCB software to design the circuit board for all 20pcs IR LEDs.

The Raspberry Pi NOIR camera will be at the center. Hope this design works.