Operation Wolf Sensor

[schifpine1]

Hello! A friend of mine sent me the sensor board out of his Operation Wolf machine to repair. It is in rough shape, so rather than try to cobble together traces, I am spinning up a new board.

Since I do not have access to the machine, I was wondering if anyone can tell me the distance from the center of the sensor to the bottom of the PCB, as show in the picture below:


I laid the board out to be very similar to the original, parts are in the same location, traces are running mostly the same as the original. But I had the thought, why not make a 21st century version of the board and go to surface mount parts where possible:

I am going to take a 2nd look at the layout, I did this really quickly. And instead of the electrolytic capacitors, I will probably parallel a few 0805 capacitors instead, as there is plenty of room. The surface mount design should be better for vibration too.

I will be making a few of these, not sure which version yet, but I may need someone to Guinea pig one of these in a working machine for me, so I know if I send it to my friend it should work unless there is another issue with his machine. Looking forward to your feedback.

 

[Khatru311]

The lords work.

 

[schifpine1]

Maybe this is a known error, does anyone else think the original schematic for the gun sensor board shows D1 (photodiode) as backwards?


From images I can find of good boards on the internet, is appears the cathode is going to ground.

 

[toledoflyer]

Maybe this is a known error, does anyone else think the original schematic for the gun sensor board shows D1 (photodiode) as backwards?
View attachment 717231

From images I can find of good boards on the internet, is appears the cathode is going to ground.

Photodiodes can be used in two modes PV PhotoVoltaic and PC PhotoConductive. That circuit is setup in PV mode since there is no bias current. In PV mode the photodiode will generate a voltage across it in a reverse bias. So short answer NO it's not shown incorrectly.

 

[schifpine1]

Photodiodes can be used in two modes PV PhotoVoltaic and PC PhotoConductive. That circuit is setup in PV mode since there is no bias current. In PV mode the photodiode will generate a voltage across it in a reverse bias. So short answer NO it's not shown incorrectly.

Thanks for the info! I am still a bit confused. SP-3ML datasheet shows the anode on the tab side which is shown soldered to R1/C3 in this picture:

I do agree that the schematic is drawn correctly, but why do we see the cathode to ground on the actual boards? Maybe they wanted to change the polarity of the voltage produced by the photodiode? How one would know that the diode should actually be installed backwards when looking at the schematic?

 

[schifpine1]

Finished board, just need to install the photodiode:

 

[boycer]

Still make these?