TV-B-Gone Mod - Please Help.

[wagnerpj]

I would like to mod the v1.2 TV-B-Gone to increase the range.

1) I would like to substitute four 10mm IR LEDs (940nm, Vf= 1.6V, If= 100mA) for the kit LEDs. Will the transistor driver circuit on the existing v1.2 kit be adequate to power these larger LEDs?

If not, could someone make suggestions for circuit mods to drive these LEDs.

2) Since the LEDs are only driven on an intermittent basis, how would I modify the v1.2 circuit to put out the highest (LED safe) driving current for these new LEDs?

Thanks in Advance!

[geoffn]

Hi,

(1) The transistor driver circuit should be sufficient to drive IR LEDs with the electrical characteristics you mentioned, yes. They are similar to those of the IR333-A. The bigger concern will be whether or not those 10mm LEDs will actually fit on the PCB nicely. If they're made to bend outwards (fanned out horizontally) to fit, you may get an increased angle, but at the possibly noticeable cost of a reduced range (which is not what you want), and possibly even gaps in your emitted 'triangle' of IR light.

(2) The LEDs are already being driven as hard as they can be; there are no current limiting resistors in place and the firmware uses PWM out of necessity since many IR-receiving devices expect a PWM signal.

Your best bet is probably to increase the power you're putting into the TVBG. The datasheet for the ATtiny85v specifies that voltages as high as 5.5v may be used. My own modified TVBG build uses a 800mAh 3.7v Li-Ion cell with great results (and only 3 LEDs, not 4).

I should mention that at extreme distances, the power of your TVBG may begin to matter much less than your aim.

Hope that helps.