| Author | Message | ||
     Stephen |
Hi everyone! I have been reading through and have read 90% of the projects that scitoys have created and im amazed at how well each one is documented. The project i wanted to do is simply have an L.E.D connected to a serial cable and blink morse code. So exactly the same as the final computer controlled transmitter except no oscilator. I grabbed an L.E.D from an old computer system and pulled of the little jumper thing at the end so i just had to wires from the L.E.D and then pulled apart an old serial cable, so i had 9 wires. I then searched google and found a site which told me which colour cable was for which pin. I thought it would then be a simply process of running the morse code program that is available for download on the scitoys website on repeat message and then match up the wires but the best i can do is get power to the L.E.D permantly but not to flash with the text... if anyone could tell me which pins i need to connect the two wires too from the L.E.D then i would be most greatful. Thanks | ||
| Simon Quellen Field (Sfield) |
If you look at the Computer Controlled Transmitter web page, under the heading "Some nicer packaging", you will see a version that powers the oscillator, and a blue LED at the same time. In that section is a schematic that shows the LED connecting to pin 7 and pin 5 of the 9 pin connector. You can also connect it to pin 4 and pin 5, instead of the oscillator. If the LED is staying lit, try reversing it. The voltages on those pins reverse when the signals are sent, instead of just turning on and off. In other words, the voltage between pin 4 and pin 5 is something like 12 volts when the LED is on, and -12 volts when it is off. | ||
| Stephen |
Thanks for the fast reply simon, I understand that you must get annoyed with people asking questions which you have already explained in your previous posts/write ups. I have read your write up on the computer controlled transmitter SOOO many times now and I never get bored of it. So if I connect the LED to pin 4 + 5 and run your morse code program and put it on repeat then the LED should flash on and off right... ? Thanks Last night I thought I would make a little toy that hooks upto the USB port, so it was basically just a fan/light with a little on/off button, it all worked good until i accidently let the wires touch each other and they blew all my usb ports  but luckily I managed to hookup some front end USB ports to the motherboard so its not that big a problem. THanks for the fast reply! | ||
| Stephen |
I just re-read your post, How does it reverse the voltage? Is it controlled by the motherboard? So while the voltage is reversed it would cause the LED not to work or to work and then the other way oposite, it makes sense now  | ||
| Stephen |
Im really having no luck, i have tried connecting the LED to pin 4 + 5 and then 7 + 5 and no luck either way round i put the LED. The best i can do is get it to stay permantly on. | ||
| Simon Quellen Field (Sfield) |
You might want to test your serial port to make sure it works with other equipment. The other thing to check is to make sure you have the right pins. You might be looking "out" of the connector instead of looking "in" when you interpret the diagram. Use a voltmeter to check the connection. When playing around with USB ports, you might consider getting a cheap add-in card, so that if you damage it, it is easy to replace. Damaging the motherboard USB hardware can be more expensive. While RS232 ports are designed to be tolerant of short circuits (they don't carry much current), USB ports are designed to power devices, and shorting a power supply is usually a bad idea. You can also get a cheap serial card, or a USB-to-serial device to help isolate your computer from your experiments. | ||
| Stephen |
Thanks for your continued support simon! The serial port works fine, I hooked up a cable between the pc and the laptop and used hyperterminal to test and it worked fine. I used the diagram on the computer transmitter page to do my project... I really do not understand what's going on, i tried multiple pins and the pin 4 + 5 to the LED would simply keep the LED on one way round and do nothing the other way round. Does it matter that im connecting the serial port connector direct to the machine without a cable? I agree, I should invest in a seperate pci usb card or similar if I want to experiment with USB stuff, from what I have read USB ports do carry a much higher current than serial ports and I should be more careful since I now have no USB ports working at the back of my system :'(. | ||
| Stephend |
Simon if you still have your kit would you mind trying to just hookup a simply LED and tell me if you have any success and on which pin please? Thanks | ||
| Simon Quellen Field (Sfield) |
Radio Shack (and other places) sell little gadgets that have LEDs in them to show you which pins are "on" and which are "off" on a serial port. They are nothing much more than two connectors and some LEDs. My transmitter, with the blue LED, works fine whether connected with a cable, or directly to the back of the computer. If you use a "gender mender" cable, you can plug one end into the computer, and the other end will have holes in it, where you can insert the leads of the LED. These holes will have faint, tiny raised numbers next to them to show you which pin is which. Hyperterminal will still work if you have turned off hardware handshaking, even if the DTR and RTS pins are bad. Make sure you have hardware handshaking turned on before you run the test. If you use the Radio Shack device, you will see the hardware handshaking lights turn on when you start hyperterminal. | ||
| Stephen |
FINALLY SUCCESS!!!! Pin 5 and pin 7 when connected to hyper terminal will flash if a character is sent! Im very happy :D Ill more than likely have more to say soon Thanks simon! | ||
| stephen |
IM GOING CRAZY, IT WORKED but now doesnt! I wrote down which cable went to which pin so im guessing it mnust be a software difference thats making it not work now :S | ||
| Graham |
hi. i would like to make the Building a computer controlled transmitter project, however, you do not ship to the United Kingdom. can u reccomend any good places to get the parts for this project. | ||
| Simon Quellen Field (Sfield) |
We ship all over the world. You seem to have missed "Great Britain & Northern Ireland" when looking at the huge list of countries we ship to. |
