In order to consistently photograph something like milk drops the usual method uses a high-end camera ($500 and up), Speedlite flash ($300 and up) and an optical electronic delayed flash trigger ($120 and up).
There are lots of DIY circuits for this purpose, but they still require a good camera and a high-end flash unit.
And you have to manually open the shutter requiring the photo to be taken in a darkened room.
Here's how you can consistently take the same photos with an simple circuit, inexpensive point and shoot camera, no additional flash unit, all without fumbling around in the dark.
The video above shows the ease of use of this rig and some of the better splashes of the hundreds that I've captured.
I've concentrated on milk drops, but this can be used for many different things. The separation between the laser and the detector could be hundreds of feet apart, or bouncing off mirrors...
I got the following at my local Dollar store (each item was actually $1.25: talk about misleading advertising!)
Self-Adhesive backed Velcro
Small picture frame (for the plate glass insert)
Eye drops (for the dropper bottle. I poured out the contents as I believe anything
purchased at a dollar store should never be applied to one's eyeballs!)
Here's what you'll need for the circuit (I don't think your local dollar store will have these so you might try an electronics distributor like Digi-Key):
Part/ValueDigi-Key Part #
4 .01 uF 50V metal film CapsP4513-ND
3 1.0 uF 50V Ceramic CapsBC1162CT-ND
1 10 uF 35V Electrolytic CapP818-ND 1 1K Ohms 1/4 W resistor1.0KQBK-ND
1 22K Ohms 1/4 W resistor22KQBK-ND
2 120 Ohms 1/4 W resistors120KQBK-ND
2 200 K Ohms .5W Multi-turn PotsCT94EW204-ND
1 Green LEDP14228-ND
1 Red LEDP14224-ND
1 LM556CN timer IC296-6504-5-ND 1 7404 inverter IC568-2921-5-ND 1 Photodiode PNZ300F-ND
Please note that the schematic has been revised to use new photodiode.