Invention Lab — Powered by RadioShack®

Every hobbyist needs one of these; an ATX power supply made into an inexpensive ben top power supply. Capable of supplying a number of voltages, this simple project will be a center piece for any do-it-yourselfist needing a solution to their power needs in testing and fabricating other projects.

On a standard ATX power supply, the PS_ON pin can be identified by the green wire, number 16. When a computer is turned on, this pin is tied low and gives the PSU a signal to turn on its main voltages. Prior to activating the main voltages, pin 9 being +5VSB and purple, provides a constant +5VDC as a standby voltage and can be capable of delivering an amp or more while main voltage is off. It may be useful as an indicator of AC power or an always-on supply for small loads. Other voltages provided include +3.3, +5 main, +12, -12, and -5. Combining these will yield various other voltages that can be calculated by absolute potential.- ted

My friend owns an acupuncture business and runs it himself. He bought one of those wireless (sonic proximity detector) doorbells that rings when someone walks through the door that you have mounted it next to but found that the loud ringing was disturbing his patients.

My solution was to create a device that will flash a backlit sign to alert him when someone enters or exits his business. The wireless (RF) sign will be mounted in his treatment room/s and the detector will be mounted at the main entrance.

- The detector uses a 741 OP amp as a standard break beam detector.
- The output is fed into the parallel port of a PC running any linux 2.4+ kernel.
- The PC runs a very simple C++ application that monitors the LPT port for state changes.
- A prefabricated (rc car) transmitter is connected to another pin from the LPT port.
- When a state change is detected the application alternates high and lows to the transmitter which causes it to turn on and off.
- The transmitter is a two channel (forward/backward, left/right) with four output states. With two small rectifiers you can drive four digital inputs. I.E. Four different color leds or four signs that mean different things.
- The receiver (located in another room) is used to directly drive the LED’s that backlight the sign.

- By using an additional breakbeam detector you could position them so that you could discern the number of people entering and the direction of travel (ingress or egress) and flash of illuminate as appropriate.
- The timing and interval of the illumination is directly driven by the transmitter which in turn is controlled by the LPT port which is controlled by the application.

Linux Application:

/*
This application is enough to get you started. It contains code that will control the output of the data pins on a LPT port. If your IO address is different you’ll have to change this.

This app provides only enough functionality to manually output values to the parallel port. To make it truely useful you would need to create a loop that reads the value of the port until the input value changes. When the input changes you can then automate the output state changes.

Make sure you know which pins are used for what, and that you protect your ins and outs with diodes. (I.E. Protect the output of your detector circuit (that the app “reads” because it is possible to “write” (turn on) to the pin that it is connected to.)
*/

#include
#include
#include
#include
#include

#define BASEPORT 0×378 /* lp1 */

void pulse(int iteration, int duration);

using namespace std;

int main()
{

int iteration,duration;
iteration = 0;
duration = 0;

system(”clear”);
cout<>iteration;
system(”clear”);
cout<>duration;
pulse(iteration,duration);
exit(0);
}

void pulse(int iteration, int duration)
{
if (ioperm(BASEPORT, 3, 1))
{
perror(”ioperm”);
exit(1);
}
for (int x=0;x<iteration;x++)
{
outb(255, BASEPORT);
usleep(duration * 1000);
outb(0, BASEPORT);
usleep(duration * 1000);
}

//This is how you would read from the port
/*printf(”status: %d\n”, inb(BASEPORT + 1));*/

if (ioperm(BASEPORT, 3, 0))
{
perror(”ioperm”);
exit(1);
}
}

I got cheated on a poor motherboard that used up a new C2032 battery every month. Coincidentally my next door neighbor is a phone surveyor and one of her company’s contracts was dealing with the a motherboard that ate the CMOS battery. It wasn’t a defective item, it was a defective model. I later found this mobo was sold on the internet for $15.

So I miked a used C2032 battery and found the big side of it is the same size as a penny. The small side is the same size as a dime. I found (somewhere) 2 washers that size. I drilled them with a 1/16″ hole each. I soldered on wires, red for positive and black for negative. There is a “+” on a C2032 battery so check yourself carefully. Note for anyone who wants to solder on a penny. They are copper plated zinc now and melt very easily.

I cut a disk of paper and superglued it to the penny-sized washer. Then I superglued the dime-sized washer on top.

Then I went to Radio Shack and got a battery holder for 2 D cells. I soldered the correct color coded wires to the battery holder. Remember that the outside of a battery is negative and the nipple at the center is positive. It is marked on a lot of battery packages.

Then I took a couple big sheet metal screws. At the back of a computer are the peripheral slots and filler plates for unused slots. Because so much is done by onboard chips nowadays there are always extra slots. I drilled thru the back of the battery holder into a filler plate and screwed it on. I ran the wires and the washer assembly back into the computer and plugged it into the CMOS socket. I put in 2 alkaline D cells. I taped over the batteries to keep them in the unit because they are none too secure.

I’ve only had to change my D cell CMOS batteries once in 3 years. And when I did I didn’t have to open the computer’s case.

This was very easy but we had to figure it out ourselves…

We built an AM Radio transmitter using the Electronics Lab from RadioShack. The only piece we had to buy was a 1000mhz oscillator. So it broadcast at 1000 am. FCC allows a 3 meter antenna which will give you a good range. I used a small 1/2 meter antenna (connected to the yellow wire) and it broadcast about 50 feet.

Using other parts from the kit, I also put in a pulsating light that blinks with the beat.

Attached is a photo. There is a 100UF capacitor between the oscillator and LED light.

In the photo is hooked up to my MP3 and running on 4.5 volts. I also hooked it up to my computer and could use the microphone and play things like a “disc jockey”.

RadioShack has come out with a smaller / cheaper version of Electronics lab for $50 which will probably work. I’m not sure if has the transformer on it. In my picture, that is where the MP3 player is plugged in.

Sorry I don’t have a schematic…

MP3 Player -> Transformer
Electricity (4.5 volts) -> Transformer
Transformer and Ground -> Oscillator
Oscillator->Antenna.
Oscillator->capacitor->LED

I also got a solderless “bread board” with a battery plug and it worked as well. Cheaper than the Eletronics Lab but I think the RadioShack product was worth it and got us started doing cool projects.

–Roy