Ok, I'm fairly new to electronics but already I'm getting the impulses of an evil genius. Basically what I want to do is to control my circuits with my computer. I work in the IT industry so the programming part is covered. I found two deviced at a local online suplier that look promising.

http://www.electronics123.co.za/Main.asp?D={F089554F-30C6-4E44-A486-710CA1E205E3}&PageType=Product&SKU=AD543

AND

http://www.electronics123.co.za/Main.asp?D={F089554F-30C6-4E44-A486-710CA1E205E3}&PageType=Product&SKU=VN413++++++++++

Questions are as follows:
1) Which one of these two would you recommend and why?
2) I'm assuming that because it's USB that it just pumps 5v to the device and from there on it's up to the circuit to do with it what it should. Is this basicly what the above two devices do?
3) If my assumtion on question two are correct then would fitting a simple relay on the circuit do the trick?

The whole idea behind this is for a security system and home automation.

 

The first one needs an external power supply. It is good. Not much information about the second one.

 

Any comment on my questions?

 

I can't really compare them. It does not take all the power form the USB it requires an external power supply (at least for the first device). For the first device if the relay draws less than 100mA and its coil voltage is less than 50V you can do it. Otherwise you need a transistor.

 

Ok, so I hear that by using a serial port dongle you can control things with your computer that way? http://www.geocities.com/micgm/circuit/circuit.html

Can anybody help me with this?

 

I suggest you use FT232 from FTDI as USB-serial converter, and then some ATmega or similar microcontroller to do what you exactly need. You said that you are skilled in programming, so if you choose microcontroller with enough ram, flash space and I/O ports, it can do whatever you dream of.

P.S there are also controllers with USB support, but I never used them. http://atmel.com/dyn/products/devices.asp?family_id=607

 

I'm a big fan of the USB Micro

http://usbmicro.com/

Really nice and simple, but powerful too.

 

Hi all, i m wondering how to connect an Oriental stepping motor with a driver provided. It has total of 8 signals to be manipulated. Plz recommend whether using serial or parallel port is better. Tq.

 

how does the driver work? Just a direction bit and a clock, or more elaborate signaling?

 

I have the Velleman board, but don't know anything about the other.

It basically does what it says.

I was given it as a kit a few years ago. It comes with a simple example demo GUI that lets you send and receive analog and digital IO and PWM. The demo ran on my old Win98SE system, but the DLL they provide is only designed for XP and up, which I don't have, so I was unable to program my own interfaces to it. But the demo demonstrated that the board does exactly what it was advertised to do.

From your comments I believe that you have a little to learn about hardware interfacing. Yes, the digital outputs produce 0 volts when told to go low and 5 volts when told to go high, but it may not have enough current to drive a relay directly. Plus, if you tried to drive a relay, the inductive voltage kick from the relay coil shutting off has a good chance of destroying the outputs on the Velleman board unless you know how to supress them, just to give one example of the pitfalls you may run into with this project. Not to discourage you, just pointing out that there's a lot that goes into a well-designed hardware interface.

Your question about the serial port dongle links to a parallel port, which is a different thing entirely. Both could be used to get signals in or out but you'd have to interface to them completely differently.

But be careful - if you try connecting a relay directly to your parallel port, you take the chance of destroying a port output pin from that inductive kick.

I agree with Kubeek - for an interface beginner, getting a microcontroller development kit would be a great way to get started. I'm not familiar with ATmega, but I've used the Parallax Propeller microcontroller with USB FTDI interface and it works great.

For about the same price as the Velleman board, you would be starting off with a much better platform for developing home automation/security stuff, with plenty of example projects to get you started in hardware interfacing off the microcontroller.