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Step 9Adjusting the circuit
With your drop rig in place mount the photoresistor to one of the steel brackets and the laser on the other one. Adjust the position of the laser so that the droplets fall through the beam. Adjust the position of the photoresistor so that it's illuminated with the laser.
Power up the circuit. LED1 will light up, indicating power.
Before we begin using the eye-dropper, we should set the photoresistor's sensitivity using VR1. Momentarily interrupt the beam. LED2 should blink indicating the circuit has tripped.
Adjust the sensitivity so the circuit triggers consistently. You may find ambient room light is interfering with the circuit, either preventing or causing false triggering, so you may need to dim the room lights, or mount a shade around the photoresistor.
Make sure that the delay potentiometer is set somewhere around the middle. If it's set to the very end of it's limit, the circuit won't work.
Once the circuit is working, power it down and plug the USB cable into your camera.
Turn on your Camera with CHDK running, then power-up the circuit. A 5-volt signal will be fed to the camera. Sensing that signal, the camera will pre-focus, and then it's LCD viewfinder will blank. The camera is now armed and ready, waiting for the 5 volt signal to fall to zero.
Interrupt the laser beam, and after a very short delay the camera will take a high-speed flash photo.
Interrupting the beam a second time will re-arm the camera for it's next shot. Once the circuit is working, interrupting the beam alternates between arming the camera, and tripping the shutter.
Now it's time to start spilling milk. All that's needed is to dial in the proper amount of delay.
Power up the circuit. LED1 will light up, indicating power.
Before we begin using the eye-dropper, we should set the photoresistor's sensitivity using VR1. Momentarily interrupt the beam. LED2 should blink indicating the circuit has tripped.
Adjust the sensitivity so the circuit triggers consistently. You may find ambient room light is interfering with the circuit, either preventing or causing false triggering, so you may need to dim the room lights, or mount a shade around the photoresistor.
Make sure that the delay potentiometer is set somewhere around the middle. If it's set to the very end of it's limit, the circuit won't work.
Once the circuit is working, power it down and plug the USB cable into your camera.
Turn on your Camera with CHDK running, then power-up the circuit. A 5-volt signal will be fed to the camera. Sensing that signal, the camera will pre-focus, and then it's LCD viewfinder will blank. The camera is now armed and ready, waiting for the 5 volt signal to fall to zero.
Interrupt the laser beam, and after a very short delay the camera will take a high-speed flash photo.
Interrupting the beam a second time will re-arm the camera for it's next shot. Once the circuit is working, interrupting the beam alternates between arming the camera, and tripping the shutter.
Now it's time to start spilling milk. All that's needed is to dial in the proper amount of delay.
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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.
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 ...
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?
You may also use a photodiode that is sensitive in the red to infrared range only, which will inherently filter out anything below "red" in the spectrum.