AF Assist tool v3.0 – schematic

I think I have a schematic I am happy with to drive either an LED or laser module.

The 3.3V from the camera comes from the Remote Shutter connection on the side of the camera. One of the pins puts out 3.3v continuously, and when the shutter button is 1/2 pressed, the 3.3v drops to 0v. The op-amp is a buffer to separate the camera from the circuit, and to provide no load on the camera connection.

The pnp transistor turns on when the voltage is 0Volts at the base, and turns off when the voltage starts to increase. The potentiometer injects a little voltage into the transistor allowing for some control of the brightness.

Will build this on the weekend and will comment on how well it worked out.

The op-amp is a low power op-amp (NJU7016D) which will work down to 1V. To get a constant 3V supply to the circuit I’ll use a step up DC-DC converter (893-1150-1) which will take anything from 2-6V and convert it to 3V. So I can use rechargable Ni-MH batteries without a problem. I suppose I could use Ni-MH batteries but the light output will not be as bright. Will need to test this.

If you want to try the circuit yourself, paste the following code in the Import window of this circuit simulator Circuit Simulator.

$ 1 5.0E-6 11.086722712598126 43 2.0 50
w 368 192 368 240 0
w 368 160 368 112 0
t 320 176 368 176 0 -1 -0.5032939315847691 -0.6509749638808473 100.0
R 368 112 368 80 0 0 40.0 3.0 0.0 0.0 0.5
162 368 240 368 288 1 2.1024259 1.0 0.0 0.0
r 368 288 448 288 0 50.0
r 320 176 256 176 0 10000.0
a 112 128 208 128 1 3.0 0.0 1000000.0
g 448 288 448 320 0
R 112 112 112 32 0 0 40.0 0.0 0.0 0.0 0.5
174 224 240 288 240 0 1000.0 0.5 Resistance
g 288 240 288 288 0
R 224 240 224 288 0 0 40.0 0.0 0.0 0.0 0.5
x 239 271 282 274 0 12 dimmer
x 122 55 199 58 0 12 From Camera
x 387 86 409 90 0 18 V+
x 220 319 242 323 0 18 V+
x 380 182 405 185 0 12 PNP
w 112 144 112 192 0
w 208 128 208 192 0
w 208 192 112 192 0
w 208 128 256 128 0
d 256 176 256 128 1 0.805904783
w 256 224 256 176 0

New circuit:


$ 1 5.0E-6 11.086722712598126 64 2.0 50
w 384 192 384 240 0
w 384 160 384 112 0
t 336 176 384 176 0 -1 0.08720318604919175 -0.5937806404098391 100.0
R 384 112 384 80 0 0 40.0 2.4 0.0 0.0 0.5
162 384 240 384 288 1 2.1024259 1.0 0.0 0.0
r 384 288 464 288 0 10.0
r 336 176 272 176 0 10000.0
a 64 128 160 128 1 3.0 0.0 1000000.0
g 464 288 464 320 0
R 64 112 64 32 0 0 40.0 0.0 0.0 0.0 0.5
x 74 55 151 58 0 12 From Camera
x 403 86 425 90 0 18 V+
x 396 182 421 185 0 12 PNP
w 64 144 64 192 0
w 160 128 160 192 0
w 160 192 64 192 0
w 160 128 208 128 0
d 272 176 272 128 1 0.805904783
w 80 288 80 320 0
w 160 320 160 272 0
a 80 272 160 272 1 15.0 -15.0 1000000.0
w 240 128 272 128 0
R 304 272 304 304 0 0 40.0 2.4 0.0 0.0 0.5
r 240 272 304 272 0 10000.0
d 240 272 160 272 1 0.805904783
w 224 192 240 272 0
t 224 192 224 128 0 -1 0.5873440446885277 -0.47840262748946916 100.0
g 80 256 80 224 0
r 80 320 160 320 0 100.0
r 80 320 80 352 0 100000.0
R 80 352 160 352 0 0 40.0 3.2 0.0 0.0 0.5

One thought on “AF Assist tool v3.0 – schematic

  1. Pingback: AF assist tool v3.0 – complete | adrian's domain

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