James’ Blog

Strobing Electronics

Posted on February 18th, 2007 by James.
Categories: General.

Way back in the mists of time my friend Darren sent me this link to a guy who’d made a “Time Fountain” by strobing some LEDs at some dripping water. It looks pretty cool, so I thought I’d have a go at making my own one. Unfortunately his circuit uses some crazy complicated looking programmable PIC processor.. So I decided to make something a little cheaper and simpler. It all started with a cunning plan scribbled on the back on an old envelope

As you can see here the plan is to use a 59pence 555 timer chip and a couple of variable potentiometers to control the strobing effect. On the left is a rough circuit diagram. If you tilt your head to the right you can see that the other scribblings are designs for a thing to make the water drip.

A quick trip to maplin and the stage is set

I don’t know why, but I always arrange parts into a smiley face before I start 🙂 Just out of shot of the picture is a little plastic bag with an old broken mobile phone car charger. I grabbed it out of the shed just in case any of the bits would come in handy.. How right I was!

Everything went pretty much according to plan sticking the bits together. I had my multimeter hooked up to the output to test it was working ok, and it looked great. I had a controllable pulse coming out! Then I hooked up one of the LEDs and it blew almost immediately! Opps.. A quick check on the website later and I found that my LEDs are only rated up to 5V!.. and I’m using a 9V battery. It was now after 6pm on a Sunday so Maplin is shut. Where on earth am I going to find a voltage regulator?! .. Then I looked over at my busted mobile charger. Sitting right in the middle was a voltage regulator!! I looked up the part number on the net and it is designed to give a stable 5V output! How lucky is that!!

I wired it up to the output and my little LED strobes perfectly! 🙂 .. The MAX voltage the LED can take is 5V and the regulator produces 5V, so I’m running the LED right on it’s limit and if you strobe it really really fast until it’s almost solid, it gets rather hot, so I’m going to have to replace the regulator in the final version, but for now it proves it works 🙂

So after a bit of fun soldering things together we have this:

Obviously you can’t see it in a static picture, but this LED is strobing like a crazy mo fo.. and most importantly, one of the variable potentiometers controls the light pulse length and the other controls the delay between pulses. Which means once I get this thing hooked up properly, one will make the drops look longer or shorter and the other will make them move forward or backwards through time (relatively of course!)

I did a little test using the tap in the kitchen to make the drips and it looks promising, but what has become very clear is that I need to make very very consistent water drops. The drips coming from my kitchen tap are way too random. So stage two of this project is to build something that makes quite fast, small identical water drops!

If anyone has any suggestions, I’m open!

Currently my plan is to make something similar to a heart bypass machine to pump the water. A single flexible tube from the water basin up to the drip point, then in the middle have a motor with some rollers one it to squeeze the pipe and pump the water up. This means all the motor parts are kept out of the water and the flow should be easily controlled by the motor speed. Plan #2 is to make an Archimedes screw, but then I may have to have moving parts under water which I don’t like.

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