OT Kinda - But it is Hardware Dev Related

**veedubya** · 01-18-2007, 09:11 PM

OK I am so bored. And I have a few things to mess with, take part etc...

My list is a 1:8 scale RC Car, a spare laptop and a USB Camera.... I was looking one day and ran across a PC Controlled RC Car, after more searching I must have been under a rock... Everywhere! Using the parallel port D1-D8 and a ground you can sent 5V to a NPN transistor which in turns acts like a switch. As i stated this is nothing new, BUT my idea was to place the laptop on the RC Car and run very basic VB Program to send the voltage to the correct data line:

Forward - Reverse - Left - Right
and use the USB Cam for visuals. Now I believe i am right in thinking i can put a wireless card in the RC laptop and a Wireless card in the control PC and ad-hoc them and use VNC to see/control the laptop PC. Thus extending my range to the range of the wireless vs. the handheld control thingie.

2 questions:

1. Is there a IC Chip that contains 4 or 8 NPNs? This would make the parallel interface easier to build.
2. Anyone willing to assist me in a rather simple VB Program to control the datalines. My thought were one for each direction mapped to arrow keys and the other 4 for extras - possible pan/tilt - small horn - anything small i could activate with a switch.

I maybe crazy - but many many years ago i decided to put a computer in a 1971 VW Beetle and well does that make me crazy

Thanks in advance.

**Chris31** · 01-19-2007, 09:35 PM

1) Yes the ULN2803 and many other more will interface directly to the parallel port.
http://www.st.com/stonline/books/pdf/docs/1536.pdf

2) Not me, Im too busy with my own things, but it shouldnt be that hard. You just basically send a byte to the port. Before you do so you read its state first then mask off the unwanted bits before sending the new byte so that the rest of the line is not effected.

As for the drivers, I dont know how you want to control the RC car, because all it does is ground or disconnect its output when you apply 5V/0V to its input. Of course you can easily drive the relays using this IC. You basically created a parallel controlled relay card.

**veedubya** · 01-23-2007, 07:36 PM

OK thanks!

I am trying to wrap my old feeble mind around this.

I am attaching a simple circuit in hopes the following makes sense.

Basically the NPN trans. replaces the actual switch in the RC controller.
5V is supplied by the Parallel Port to the BASE, which causes the collector and emitter to close, (ACTING AS A SWITCH)

So with that stated. Am I correct in my thinking of the below circuit.

If i bring Pin 1 High (5V) would that cause pin 16 and ground to open and turn the LED on?

**Chris31** · 01-25-2007, 10:53 PM

The chip does not need a +5v supply, it only need the ground, it goes like this >>>

(PIN 1 - PIN 8) are the control inputs
(PIN 11 - PIN 18) are the ouputs
(PIN 9) is the ground
(PIN 10) Free wheels, ignore this.

Connect all the LEDs with limiting resistor like this >>>

(+5V RAIL) ---[220]---|>|---> (CHIP PIN 11-18)

(0v) ---> (CHIP PIN 9)

(LPT D0-D7) ---> (CHIP PIN 1-8)

You can replace the LEDs and resistor with relays instead. The + supply to the relays doesnt have to be 5V, you can use 12V relays. Dont forget to put a diode across the relay coil to avoid damaging the output of the ULN.

Before you connect this to your PC make sure each line works but putting a +5V/0V on each inputs and see if the LEDs/relays turn on or off. (0 or 5V only into the inputs)

Thats it...

**Enforcer** · 01-25-2007, 11:05 PM

Velleman K8055 USB I/O Board Extension plugin

might be easier to hook up.

also observation on the VNC thing. I'm not sure how VNC copes with video, but whenever I'v tried it, it won't send the video to the remote PC.

**veedubya** · 01-25-2007, 11:21 PM

Chris - what? no 5V? uhh am i wrong in thinking that the Data lines from the parallel port go high = 5V and thats what triggers the NPN to switch on and complete the circuit on the RC controller.

Not sure if you read my OP but why do I need 12V relays.

I have tested with seperate NPNs and i had my RC car plowing into the wall with the laptop taking a ride. This was controlled via VNC from main computer sans the video.

Enforcer - I have had good luck with VNC and video at work.

**Chris31** · 01-26-2007, 02:29 AM

Originally Posted by veedubya

Chris - what? no 5V? uhh am i wrong in thinking that the Data lines from the parallel port go high = 5V and thats what triggers the NPN to switch on and complete the circuit on the RC controller.

Not sure if you read my OP but why do I need 12V relays.

I have tested with seperate NPNs and i had my RC car plowing into the wall with the laptop taking a ride. This was controlled via VNC from main computer sans the video.

Enforcer - I have had good luck with VNC and video at work.

Just follow this circuit, its basically the same as the one I have described above >>>

http://www.southwest.com.au/~jfuller/sio5works.htm

No, the ULN chip does not need a supply, because all it does is sink its output to the ground when you apply the +5v to its input. Dont get confused with the 5V you apply to the chips input with the chips supply voltage. Notice there is no connection for the +5V supply on the ULN.

As for the relay, I suggest it cause you cant exactly do much with LEDs to control the RC car. If all you want is turning the LEDs on/off yes you can connect them directly to the LPT port no need for this drivers, LEDs with limiting resistors. Of course it is always better to use a buffer to avoid over loading the LPT port.

The ULN chip is typically used to drives relays.

or maybe I didnt read your original post properly

**veedubya** · 01-26-2007, 10:30 AM

Its all good now... If you look at my circuit, dont read too much into it

It more a proof of concept. The LED and is more the RC controller telling RC Car to move on way or another, the connection point from the LED circuit and chip is the NO Switch mech. inside the RC Controller.

I have found software with ios.dll i think that allows controlling the LPT Data lines in XP. and it works well.

LIke i stated in OP i have tested this with seperate NPN Transistors but thought a chip with many in it would make an easier circuit.

We are on the same page now.

Thanks for the input, I just purchased a DB25 breadboard componenet, I will continue to test/play until that comes in,