2001 A Sneaky Cat

In the foreground is Candy, The other cat is Jack a.k.a Jack "The Tripper". Candy is vary skittish, She stays in our back room. We are trying to get them to tolerate each other. So every day or so I let them get together, while I watch to make sure they don't beat the crap out of each other. This is generally how the encounters go down.

Also everything is better with dramatic music.


Curiosity Heat Shield Descent Stabilized.

  Man what a pain that was, getting the frame rate right and tracking the heat shield as it got smaller and smaller. I lost it a couple of times and had to redo it 3. I could not track it at the last few seconds before impact and added the JPL enhanced closeup video at the approximate time it impacted.

Forgot to mention I did each frame by hand.


Building an 18 Volt Power supply for Cordless tools

Several years ago my brother acquired a cordless band saw/pipe cutter. The batteries died and although I do not use it very often it would be nice to have it in working condition. A replacement battery is $61, rebuilding the batteries would cost $39. The alternative is to build a power supply. I did some research online and with the help of people on the badcaps.net forum I built one.

The parts list is as follows:
1 - transformer 120v in 16v out, I do not have the amp ratings for it.
1 - 25 amp Bridge rectifier
1 - 10,000uf 35v or higher electrolytic capacitor.
      You can use 3 - 3300uf 35v caps in parallel or 2 - 4700uf to 5000uf 35v caps in parallel.
1 - 10amp 3 prong power cord
1 - 20 amp fuse
1 - toggle switch
5 amp fuse or circuit breaker for 115V line voltage
1 - LED
1 - 270-500 ohm 2 watt bleeder resistor
misc wire that can handle 20amps.

The transformer was pulled from an APC 400 BackUPS (you can find them sometimes at Goodwill), Its input was 120v, and there were 3 wires for output,  yellow, white, and purple. Voltage from yellow to purple and white to purple was about 8 volts. Voltage from white to yellow was 16 volts (just what I needed). The first rectifier I used was pulled from an electric wheel chair charger, but I changed it to one I purchased that had the flat quick connectors. Other sources for the rectifier are computer power supplies, you can get the flat inline ones that range from 4 to 8 amps depending on the PS. The capacitor I had to buy, since I needed the voltage rating to be greater than 25v. All the ones I had were 16v. You can  use a capacitor with a higher voltage rating but not lower. Since we are dealing with 22 volts a 25v cap is just a little to close, so a 35v is better. The one I used is 50v. Wiring is done per this schematic:

I wired a standard 10 amp power cord to the input of the transformer and plugged the yellow and white wires directly in to the rectifier. I ran 2 wires from the dc output to the capacitor (making sure to keep the polarity correct). From the capacitor I ran the wire through another 10 amp cord to the contacts inside the battery cartridge (after removing the dead batteries). This way If needed I can still use batteries if I want to.
The results look like this:
I mounted everything temporarily to a board. With the band saw not running, voltage from the output is 22vdc, while it is running the voltage reads 18vdc. I will mount the power supply in a box and add a switch, light, and fuses. At this time I am not sure what the maximum amperage draw is, I will have to check that and install the appropriate fuses. I did not install the bleeder resistor at this time, and I'm not really sure if one is needed. It would be installed across the leads on the capacitor if I do. The capacitor and rectifier cost $20, I could have gotten them cheaper if I ordered them on line, but did not want to wait for them.

I could not find a box to mount it in, so I re-used the UPS case. I was able to re-use the original circuit breaker, and switch. I also added a 20 amp fuse on the DC side, and an LED on the front of the case.

The rectifier is mounted to a piece of aluminum (with heat sink compound) that I had to install to properly brace the front and rear panels, since the original circuit board was used for that.

The LED is connected to a 270 ohm 5 watt resistor. It bleeds the capacitor down to a safe voltage in about 25 seconds when power is turned off. The LED will stay dimly lit for some time after that. Pressing the switch on the band saw will make the LED go out if power is off. The LED does NOT dim when the band saw is in use.
I may mount a fan in it at a later time if I find there are any heat issues. I doubt there will be as I will not be using it for continuous duty.


Converting a 9.6 volt Makita Drill from Nicad to LIPO

I have had an old 9.6 volt Makita drill since around 1989 or 1990. I bought it when I was an A&P. Since then I have replaced the batteries about 4 times. I recently bought an 18v Lithium ion Makita. I wanted to continue to use the old Makita but did not want to buy any more batteries as they are kind of pricey and do not last long. I have seen several videos on the internet on connecting RC LIPO batteries to the Makita and they work fine.... EXCEPT that none of the people who do this take any precautions to prevent over discharging the LIPO batteries. LIPO cells do not like to be discharged below 2.7 volts per cell. If you do that you kill them. The good thing about them is that they are relatively cheap. You can pick them up for $15 to $20 for an 1800mah or 2200mah battery respectively. this is 200 to 500 mah more than the replacement batteries from Makita which are 1300mah to 2000mah.

My choices for not over discharging them were to make a circuit the cut off the voltage at around 9 volts or set off an alarm when they got down to 9 volts. I went with the latter as it was easier to build and some of the parts can be scrounged from an old computer power supply. The parts list is as follows:
1 - Makita drill
1 - 4.7k resistor
1 - 47k resistor
1 - 1k resistor
1 - 18k resistor
1 - LED any color
1 - LM393 (pulled from the old Power supply)
1 - TL431 (or a KA431 pulled from the old PS, I got 3)
1 - Piezo buzzer (not a speaker a BUZZER it will have all the buzzer circuitry built-in)
1 set of Deans connectors (male for the drill and female for the battery)
at least 1 - 3 cell LIPO battery around 1800 to 2200 mah (any bigger will not fit). Do not use any more or less celled batteries as this circuit will not work right for them.

1 - Piezo buzzer (not a speaker a BUZZER it will have all the buzzer circuitry built-in) 
1 - variable voltage dc power supply or a 9 volt battery that has been discharge to 9v or less, and 1 good 9v battery.

This Schematic:

 I started by building the circuit on a breadboard. I used the variable DC PS to make sure it worked. then put the circuit together by just soldering the components to each other. It's ugly but it works.
Next I encased the circuit in epoxy so that it can take abuse.
After each step I made sure it still worked.Then I mounted everything in the Makita.
I drilled a hole in the top center for the LED carefully routed the wires around the motor adding extra heat shrink or hot glue in places where the motor might rub its connectors on the new wiring (nothing really prevents the motor from turning slightly and it would eventually cut through the wires. The piezo buzzer fits but does not work as it is pinched too tightly when the case is closed (it worked outside the case). I will have to find a smaller one. The pizeo buzzer is attached to the positive side of the LED and to pin 1 of the LM393. The one I have handles something like 3 to 18 volts so the 7+ volts there works fine. I had some trouble getting the case closed again as the gears and such moved, but I did get it closed. So now when the drill runs the battery down to around 9.1 volts the LED starts to light up and gets brightest when it is almost exactly 9v. The buzzer will sound too. I added the buzzer since, if the drill were left unattended the under current circuit would slowly run the battery down and I wanted an audible warning to remind me to unplug the battery. As an added bonus when the drill is started the LED flashes once, this is nice as it lets you know the circuit works. It works fine as you can see in the video.

If your a wuss you could just order one of these and plug it in to the charging port of the battery. WUSS!