Instructables
Picture of Laser Triggered High-Speed Photography
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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...


Thanks, and have fun spilling milk!

-Brett @ SaskView

Step 1: Materials

I got the following at my local Dollar store (each item was actually $1.25: talk about misleading advertising!)

Laser pointer
Door chime
USB Cable
Magnets
Clamp
Shelf brackets
Mini-tripod
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/Value                                                               Digi-Key Part #

 

4  .01 uF 50V metal film Caps                                  P4513-ND
3  1.0 uF 50V Ceramic Caps                                   
BC1162CT-ND        
1  10 uF 35V Electrolytic Cap                                 
P818-ND
1  1K Ohms 1/4 W resistor                                     1.0KQBK-ND
1  22K Ohms 1/4 W resistor                                    22KQBK-ND
2  120 Ohms 1/4 W resistors                                  120KQBK-ND
2  200 K Ohms .5W Multi-turn Pots                         CT94EW204-ND
1 Green LED                                                          P14228-ND
1 Red LED                                                             P14224-ND
1 LM556CN timer IC                                               
296-6504-5-ND
1 7404 inverter IC                                                    568-2921-5-ND
1 Photodiode                                                                              PNZ300F-ND



Please note that the schematic has been revised to use new photodiode.
 
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Frivolous Engineering (author) 1 year ago
Hey Redrua:
1: Photo-resistors are much easier to location/purchase, but they aren't as responsive/fast as diodes. It's your choice what to use.

2. The type of cap doesn't matter (except for price) as long as the value is correct. What type of cap you use depends on price/availability.

3. 220K pots should work. Multi-turn one are preferable because you have finer adjustment compared to a single-turn pot.

Hope this answers your question!
redrua1 year ago
I have some questions.
First question is: In step 3 you told that schematic revised for photo resistor. I went to a electronic component store bought everything but the photodiode. Then I checked the schematic and saw that you used photodiode (sharp BS120R0F) in it. Should I use my photo resistor instead of photodiode or should I buy a photodiode?

Second question is: I am not a electronic tech guy or something like that. I am just wondering why you used differend type of caps? (ceramic, metal film, electroylitic) when I was at component store they told me that they don’t have ceramic ones. I thought that they all are caps and told them ok give me what you have. Their capacity are same. Now I am not sure about what I did. Will this cause a problem or not?

Third question is : I get trimpots but they do not look like the ones on your photo and they are 220K ( they have only these). Is it ok?

As I said I am not a electronic guy. I asked these questions to people working at shop but they said they can not give advice because they don’t want to be responsible. And that store is the only one in this city. I don’t care about the prices of the components (a few bucks) or price of camera (it is toy for my kid, bought for a few bucks from someone), I just want to take these photos. I just want to do it right. I will be glad if you help me.
dikenn2 years ago
Does this cirquit triggered external flash? I have a DSLR and I want to control my external flash with this cirquit. Is that possible?
Frivolous Engineering (author)  dikenn2 years ago
No, but it shouldn't be too hard to modify the circuit to drive an external flash.

Depends on the flash, new one use low voltage for the trigger circuit and can be interfaced very easily.

If you have an older flash, you will have to add an SCR to the circuit . It's to isolate the high voltage that the Flash's trigger circuit uses. Some older units have a couple hundred volts DC at the hot-shoe contacts.
What is SCR?. Sorry for my ignorance.
Frivolous Engineering (author)  dikenn2 years ago
Kind of a transistor.
squiggy22 years ago
OMG snap we used the same background music in our instructables! XD
Mine is http://www.instructables.com/id/Melody-Muffs-The-Real-Mans-Headphones
hella cool idea btw :P
Frivolous Engineering (author)  squiggy22 years ago
Great minds think alike! Excellent 'ible BTW.
lukeD3 years ago
will this work with a canon eos 350D? (digital rebel xt)
Frivolous Engineering (author)  lukeD3 years ago
I don't think so, it's not on the list of CHDK list.
drivera13 years ago
AMIGO NO E PODIDO HASER TRABAJAR EL ESQUEMA SIME PODRIAS DECIR COMO BAN LAS DOS PIEZAS DE (200KPHMS .5W MULTI TURN POT)
SaskView, you bewilder me.

-TheWaddleWaaddle
Can I do this with a Kodak EasyShare CX6230?
No, CHDK only works on certain Canon cameras.
ohhh... :-(
Mdob3 years ago
I've got one question for this. Is it possible that I could substitute the laser for an IR Led? I have a photodiode that I have used in the past with infrared Leds and it has worked wonderfully. I was thinking that a decreased distance wouldn't matter as long as the milk drop (or object) fell in between the Led/laser and the photodiode. I'm just trying to make this on the cheap and I don't have a laser but I do have an IR led, any response would be helpful. :)
Frivolous Engineering (author)  Mdob3 years ago
That should work fine.
Thanks for the info and the speedy reply :)
Mdob Mdob3 years ago
Sorry, I have one more question. Would these (http://search.digikey.com/scripts/DkSearch/dksus.dll?Detail&itemSeq=95160176&uq=634304685562081024) photodiodes work? They appear to be the same except in cost and their micro amp output (7uA [original] vs 11uA [this one]) Just want too make sure, thanks :)
Frivolous Engineering (author)  Mdob3 years ago
That link is broken, it comes up part not found...
Oops, http://search.digikey.com/scripts/DkSearch/dksus.dll?WT.z_header=search_go&lang=en&site=ca&keywords=475-2863-ND&x=0&y=0
Frivolous Engineering (author)  Mdob3 years ago
Looking at the specs, it should work.
You can check by looking at the spec sheet's graph of the 'spectral sensiivity': A red laser is about 660 nm and that falls in the middle this diodes response.
Hi there,

The part "LM556CNFS-ND" is no longer available.
Will this part from digikey suffice? "296-6504-5-ND"

Thankyou! I cant wait to make this project :D
Yep, that will work.

Take another look at the parts list and schematic: I've changed to a photodiode instead of a photoresistor.

The diode version works much better than a photoresistor. I've tried both, and I don't recommend using a photoresistor because it has a slow response and doesn't trigger reliably.

Cheers!
mickyj4 years ago
Whilst others might have made these comments else where, I have a few comments to add.
I built this rig and have yet to take any photos (At the last minute, I found out the batteries in my camera were flat - 10 minutes ago, before writing this .... talk about tension).

I know these instructables are open to interpretation and doing things your own way so I have modified this a little.
Firstly, I didn't have magnets or a glue gun. I used glue backed Velcro. I also could not find a laser pointer like the one I wanted (where I could remove the laser easily) so I bought a laser mounted on a circuit board and then shorted out the momentary switch.

Anyway, from the top of the rig down, here is what I did.

I velcro'd an empty clear plastic biscuit tray upside down to the arms holding the laser. I then used a soldering iron to poke some holes in it. I use these holes to poke the particular eye dropper through that I had.
I used the holes to get closer and closer to cutting the laser beam that is below it. To steady the eye dropper through the hole, I used an old drink container lid and some bluetack. (I will try and post photos at some stage).

I created a cross with two pieces of wood. Each 25 cm long, 4 cm high, 2 cm wide. Screwed in the middle to make the cross. On the end of one wooden beam, I screwed on two more pieces of wood which forms the arms. Each arm 9cm long, 2cm wide, 4 cm high. In one arm, I drilled a hole to poke the laser housing through (in my case 1.5 cm diameter). The laser fits snug and does not move.

My laser is attached to a battery tray that holds 4x 1.5 volt AAA batteries. I shorted out one compartment so that the pack delivered 4.5 volts. I then used a soldering iron to poke a hole through in the end unused compartment and used it to put a toggle switch in to activate the laser. I placed Velcro on the back of the battery pack and secured this to Velcro on the laser arm.

I then cut up an old milk carton and put some Velcro on this. This becomes a light guide and shield against lights from above. This is velcro'd to the second arm. Then I attached the Photodiode and leads to some Velcro and attached this to the second arm, under the milk carton.

The laser to photodiode distance is about 20 cm's which is a convenient length. The dropper is suspended about 2 Cms directly above the beam.

The arm was then G clamped to a vertical bar. This is about 46 cm above the plate I will be dropping food coloured milk onto.

I then bought a 5V usb power pack with the USB female a Type cable insert as a part of the power pack. I got a cheap USB A type to Mini USB. I cut this in 1/2. I wired the USB A type end into the circuit as the power source and can plug this into the power pack. I wired the mini usb from the circuit to the camera (just like the original instructable).

The circuit is mounted on a bread board. I used 2x temporary Zif sockets with easy release levers (18 leg) to hold the two ic's. I found some old solid core cat 5 network leads and cut them up as hook-up wire.
I used heat shrink over cable parts I needed to protect or wanted to stop moving about.

This all leads off to the A470 camera running CHDK. This is behind a small piece of glass (As recommended in the instructable) and I got some further pieces of wood to cut some notches in to hold the glass up vertical (As shown in the instructable but not discussed).

As my camera and flash both fall behind the glass, I have used a DVD cover to raise the camera and tripod to the correct level.

I then tweaked the sensitivity pot so that the drops from the dropper trigger ever time.

Now I just need some batteries and further tweaking.

Wilst I did have attery power, I also discovered setting the camera to the playback mode and triggering the laser beam, causes the camera to cycle through the images. Me thinks this might have other uses !!

Maybe setup an enterence laser to your home, someone comes through the door and a display panel cycles a picture on the camera displayed on a tv. Could be fun for things like birthdays with various images coming up on the TV.


Frivolous Engineering (author)  mickyj4 years ago
Excellent tips!
Thanks SaskView,
could this be easily set up to connect to an event counter? eg if you wanted to count how many drops went by...my application would need to count a 2-10msec break and count up to 20 such events a second....my application needs a separation of 6 m but you have answered the distance issue.

mickyj - where did you gets the bits in Oz?
Frivolous Engineering (author)  T_B_R3 years ago
Should be do-able, It's using TTL.
mickyj T_B_R3 years ago
I obtained from parts from Jaycar and the rest from Digikey (International)
mickyj mickyj3 years ago
I have found my next roadblock.

I bought new batteries, but they do not last long in the A470. Not long enough for me to get everything working. The A470 seems to drain power. I bought a power adaptor for the A470 and think I found an issue with chdk a470-101b-0.9.9-953-full.

If I power from the mains power pack without CHDK loaded, it works fine. If I use CHDK after one flash, the camera tells me it is flat, change batteries and then it shuts down the camera.

Still working on it ...
mickyj mickyj3 years ago
Using chdk 9-964 on the A470 I have found that the Override Subj. Dist. V. works. However, I have set it to zero as it zooms the camera to a place where I do not want it.
mickyj5 years ago
Maybe you should offer to sell ready made kits or bags of components on eBay ? I have been struggling to find all the parts here in Australia. I really want to give this a go but ... not until I have everything :)
Frivolous Engineering (author)  mickyj5 years ago
All the components are available at www.digikey.com and they will ship to Australia.

The photodiode is the only obscure part.   Any visible light photodiode should work.  The datasheets will usually have a graph called Relative Spectral Sensitivity.   Ask for a photodiode with a range of sensitivity that includes 650 - 670 nanometers (a red LED laser's wavelength).
Hello,

Yes, I contacted Digikey about 1 week ago (just before your post). There is about a 2-3 month delay on the same items I can't get in Australia. Hopefully I will get everything just after christmas. I will have to book mark this instrucatble and come back :)
Frivolous Engineering (author)  mickyj5 years ago
2-3 months....Ouch!

Let us know how it goes.
Still waiting on all the bits :(
kcls mickyj4 years ago
Did you get all the parts yet?
mickyj kcls4 years ago
wow, that is freaky. I just got most of the parts. You were reading my mind :)
kcls mickyj4 years ago
Oooh... Psychic. Go me!
mickyj kcls4 years ago
I have finally found time to build this. I built it on a bread board and modified the laser pointer to suit my own setup. I have yet to put a frame together to hold the laser and photoresister however, I have a working circuit which I can attach to the camera, block the beam and the flash goes off. Now it just needs to be tested.

Awesome instructable.
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