Some of you may have seen the fountain that uses strobing LEDs to make water appear like it's hovering. I am building one as my first project, with quite a few enhancements.
The original used a gold plated wire at the nozzle to detect when the water has dripped off and uses that to sync the strobing LEDs accurately.
How does this work? Can someone direct me to where I can find a thin wire with a thin gold plated connector?
Anyone have a better idea? Accuracy is key.
I of course will be posting the project up once I complete it...waiting on parts now.
A system based on the breaking of a light beam makes more sense to me that the gold wire idea.
Alternatively, I think it would be more fun anyway to have inputs to the system which allow you to vary the speed of the strobe pulses, first in coarse adjustment, then in fine adjustment. With the fine adjuster, you'll be able to make the drops freeze, or move forward slowly.... or move backwards!
For a steady stream of drops, you need a steady pressure above the nozzle. Something like a (mini!) toilet cistern with no ball valve, but with an overflow is the answer. Maintians a constant head of pressure. You don't need to waste water.... just use a small pump to feed the tank from a resevoir, and put a "pipe" (tube) between the overflow and the resevoir, so as water flows out the overflow it goes back to the resevoir.
The left part is a simple drip detector circuit. As drops touch the gold contact and fall off of it, the resistance between the contact and the water will change. Combined with the 220 kilohm resistor, a voltage shows up on the + input of the op-amp which varies according to the drop's contact area. The op-amp is configured as a simple voltage follower to reduce noise.
It is esentially how it works, but i would use it in reverse:
while the drop forms, there is a connection between the wire (note, that the wire is insulated except for the tip of it) and the drop pipe.
When the drop falls of, and before a new one forms, there is no connection.
Therefore when the input changes from high to low, the drop just started to drop.
I know there are som light beam techniques, but i'm not sure if those are actually more accurate. to me it seems that trying to capture na essentially transparent object would be harder than to measure a resistance change.
You might want to look at how water drop photography is done, i think i saw some circuits for automated triggers for that.
I used an IR beam to measure drops of water for some chaos experiments about 20 years ago. This is the set up I used. Note you get a double pulse as the water droplet passes the sensor.
Thanks Grumpy_Mike. Very informative and the bit about the double pulse was particularly interesting.
I came across these optical interrupters browsing through components:
It says forward voltage is 4.5-17v and the draw is less than 2mA. Does this mean I could connect it directly to the Adruino pins without using resistors and such?
It says forward voltage is 4.5-17v and the draw is less than 2mA. Does this mean I could connect it directly to the Adruino pins without using resistors and such?
Not forward voltage = 4.5-17v, but rather operating voltage = 4.5-17v. Yes you could power the module's Vcc line via a output pin set high, but why waste a I/O pin, just connect the devices Vcc and ground pins to the Arduino +5vdc and ground pins. The input side of this device is a IR led and that will need a series resister to limit the current to 7ma or so, say 500 ohms or so.
Especially on pointing out how unnecessary it is to use an IO port.