hey i have just rescived my Arduino board and want to use it to take High Speed photography of water drops, i have this circuit of a photogate trigger :

I have tried connecting it to arduino useing the button tutorial and code and the circuit from this post:

I can get it to detect when i pass something between the photogate and light up the LED, but the LED stays ON, shouldnt it only flash when the photogate get triggered? If i unpluck arduino from power i can get it to detect again.

Any circuit or code help would be nice.

below is there a link to some of my photos taken with my old delay unit but i want to improve it even more and i think arduino will be a great help

hope you can understand what i mean, as i dont have much experince in electronic.

Jens Erik

The SCR will latch ON

Looks like the circuit is designed to directly trigger a flashgun.

yes the output goes directly to a flashgun, or my ‘old’ delay circuit

it’s all part of a kit from : - Tools - Triggers - Make Your Own

SCR’s are better used with AC since they won’t shut off till the voltage goes near zero again. They are designed to work that way. An AC signal reaches zero 60 times per second… so it shuts off when AC is used.

You should be able to bypass the SCR and just use pin 3 of the 555 as a trigger. (remove the scr, if possible.) The 555 is running at 9V so it’s too high for the TTL input of the arduino… so uou just need to make sure the 555 pin 3 output is at max 5V TTL level. (google for TTL level converter)

That seems like an option to connect to pin, but that TTL level converter got me confused , tried to google it and it came up with alot of RS232 is it a IC or something else?
I was thinking couldnt i run the photogate at 5V?

Jens Erik

Just tried running the circuit with 5V and now it working pefectly, thanks for the hint on pin 3 on the 555 timer

Now i’m just waiting for my Solenoid valve and some Opto-isolators and i’m ready to take some highspeed photos

Jens Erik