BEAM Projects > Pummer
Final Design of Pummer
Final Design
Pummer Schematic

Pummer schmatic from
Make© magazine, Vol. 8

Circuit used: Single LED High-Efficiency Pummer
Construction Notes:
Pummers got thier name by applying a sound to the visual of the LED flashing. If it made a noise, it would sound like this: pummmmmmm.... Comes on strong, then fades away.

I free formed the circuit per the schematic, starting with the pins that are all connected. I then started adding components: the .22uf capacitors first, then the diode and resistors that are connected directly to the 74AC240 chip. The 100kOhm resistor will be mounted on the back side of the solar cell. I haven't decided on a 'look' for the final display yet (remember, the A in BEAM stands for Aestics)... We will just have to see what occurs to me at the moment.

I was originally going to use AAA rechargeable batteries, but I am going to hold these in reserve. I am going to try to get it to work with 3 of the PAS920s. They are smaller than a dime, but I am not too sure if it will keep it going long enough. Testing will tell. Other design decisions include a 2200uf capacitor for C3 (the article gives a range of 1000uf to 3300uf). It will hopefully give a satisfying burst of light.

As a side note, double check your work. I went back over the schematic and found that I had made a bad error. The picture labeled 'Start of chip soldering', the one showing the bottom (right hand side), has an error. The top-most pin on the left was not supposed to be connected to the rest. Fortunately, this was easily corrected (see the '74AC240 from bottom' picture). Once I fixed this error, I was able to power it up for some testing.

Well, the 3 PAS920s did not work out too well. I would get about 6 flashes before it was done... Not very satisfying. So, I opted for a 3.7V LiPo cellphone battery. I also changed out the 2200uF capacitor for a 3300uf capacitor (the flash seemed a bit too short). I also had to change out my original solar cell. The one in the 'Starting collection of parts' picture, lost it's solder pads while I was removing the old wires. The next replacement that I tried to use was putting out almost 5v in direct lamp light, but not enough amperage. So, I put two RU2420s in series since they put out 2.5V each at twice the amperage of the single cell. By hooking them up in series, I get 5V that will recharge the 3.7V battery. I will post more pictures when I finalize the battery and solar cell hookup.

I am still trying to work out the form it will take when done. This is the main reason I am using long wires to connect everything together. I am looking for some inspiration...

I found my inspiration on-line at Make©. Check out Zach DeBord's Pummers. They are beautiful. I used some large paperclips for the base and added a piece of brass tubing to mount the LED. I decided to use the frame a one of the leads to the LED which is why you only see one wire exiting the tube. I also opted for a blue LED, I think it looks alot better than the red one. As a side note, it is in a socket so that I can change it if I wish. The 74AC740 is just setting on top of the battery. The battery, capacitor and solar cells are held in place with hot melt glue. Since the frame is metal, I covered the back of the solar cell metal bits with a layer of hot melt glue and let it dry first. Since it is a good insulator, it protected the components mounted on the back of the solar cells and kept the frame from shorting them out. The last picture shows it pumming away! It works exactly as it should... when it gets dark, it pumms! Check out my for larger pictures. I hope you enjoyed reading this as much as I enjoyed making it.

After running the Pummer for a week, I figured I should post an update on its performance. Initially, I charged the battery from a 5v supply for testing (my work area does not get a lot of sunlight). But I am happy to report that with it in a sunny window, it pumms all night long and repeats the cycle. So it appears that my component choices worked. Have fun and build one today!

pummer parts
Starting collection of parts
PAS920 Battery
The PAS920 battery that didn't work
AC240 in work
Start of chip soldering
AC240 bottom
74AC240 from bottom
AC240 top
4AC240 from top
New battery and solar cells
New battery and solar cells
Base of Pummer
Pummer Skeleton
Battery attached
Battery attached
Solar cells attached
Solar cells attached
Final assembly
Final Assembly
Final assembly-back
Final Assembly-Back
Pumming
Pumming!

 

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