PureBasic Forums - English

Okay, I'm throwing this out hoping someone can a) point me in the right direction (so I can check against the research I have done already, to your suggestions) with some useful and practical information b) create this unit and recieve some monies for their effort (some up front and if the project goes through, more on the "back end").

Let me try to describe it well enough for folks to understand what I need...

I need a small unit (say about the same size or a bit smaller than a cable modem). This unit needs to have USB onboard, so that I can read data from it and write data to it (I need to be able to read and set the voltage, which comes from a 9-volt battery).

Now, the unit actually will send a small current out from the 9-volt, thru and to a prob on the end of a small cable (cable should be about 3 foot long). That current level I need to be able to set and read, so as to be able to capture such via code.

If someone gets gung-ho enough to build this... I'd be willing to discuss a price for it. But, I'm not looking to pay (of course) a lot. If I get paid in the end (if the project goes well, which this is the biggest hurdle), I would even shoot some more money to the person that builds such, if anyone does. Payment would be via PayPal. Payment (on top of parts.. submit a receipt for what you use and I'll review the board and unit to match parts, to make sure all is in order), including front and back end... could be either hundreds of dollars or into the 1000s. It's to early to say, as I would have to wait for the response from the buyer(s).

Please Private Message me here if you are interested. I don't want to have anyone get upset... as they start building this without talking with me first and I end up choosing another persons unit... because I did not even know you were working on this. First come... first serve on this deal.

Thanks... (hope this was not to un-proper on the forum?)

Well, depends on the specifics of the amount of current and accuracy needed I suppose, but doesn't look too hard on the face of it. A Microchip PIC controller with USB built in with a PWM output connected to a current mirror to drive out your current. If per-unit cost isn't critical but accuracy is, you could connect a D/A to the PIC for more resolution/less ripple.

Alternatively, you might be able to use a Cypress PSoC processor to do the same thing but with less parts, although I'm not 100% familiar with the capabilities of the PSoC 9-bit DAC.

The current mirror is basically a pair of back-to-back transistors connected so that one is forced to follow the other one. You can then control the current through one of them using a voltage from the processor and have the other one drive the current out. As you are using a 9-volt battery I'm guessing that you need pretty low current (ie- not some sort of mega-drive with 10s or 100s of amps of current), so its not too tricky. This current setup is similar to discrete circuits to charge batteries by varying the current at the different stages of the battery charge cycle.

Anyhow, good luck! Sounds like an interesting project.

aaron wrote:Well, depends on the specifics of the amount of current and accuracy needed I suppose, but doesn't look too hard on the face of it. A Microchip PIC controller with USB built in with a PWM output connected to a current mirror to drive out your current. If per-unit cost isn't critical but accuracy is, you could connect a D/A to the PIC for more resolution/less ripple.

Alternatively, you might be able to use a Cypress PSoC processor to do the same thing but with less parts, although I'm not 100% familiar with the capabilities of the PSoC 9-bit DAC.

The current mirror is basically a pair of back-to-back transistors connected so that one is forced to follow the other one. You can then control the current through one of them using a voltage from the processor and have the other one drive the current out. As you are using a 9-volt battery I'm guessing that you need pretty low current (ie- not some sort of mega-drive with 10s or 100s of amps of current), so its not too tricky. This current setup is similar to discrete circuits to charge batteries by varying the current at the different stages of the battery charge cycle.

Anyhow, good luck! Sounds like an interesting project.

Thanks Aaron. I spoke with my business partner today and he stated he just ordered a USB laden proto board, that comes with an assembly, where we just need to reference that in our projects and then we can communicate with the unit!

Does it sound that it could be that simple. This USB laden proto board, with assembly for communications, is only about $55.00 USD.

Thanks again Aaron.

Or buy a K8055 - USB Experiment Interface Board Kit?

You have analog and digital inputs and outputs, an easy API interface, very low cost and plenty of scope for experimental development. Having spoken to the guys at Velleman in the past I'm sure they'll even manufacture you a board to specific requirements if you need it. (Say just 4 digi-outs and nothing more)

I use one of these to control a 9v LED lighting system at home. I actually have two controller programs, one is VB6 and the other is fully PB4. The VB6 version is 'Doze-only but has full voice-activation and recognition. If only I could do the same in PB I'd dump 'Doze and run the lot under a lightwieght Linux server, but Voice Recognistion in Linux still seems to be very much a "work in progress" and swathed in smoke-and-mirrors (lack of) documentation making cross-platform code almost impossible at the moment, and also my Linx programmings skills are sorely lacking compared to just opening a .DLL and running with it.

Here is another microcontroller that might get you up & running also.
http://www.modtronix.com.au/product_inf ... cts_id=286

I have been using some pic sbc boards made by this firm & they really are quite nice units to work with. ( I have been using MPLab to program them, which is a C language but is quite easy to use for pic programming. )
All you would probably need to do is use 1 of the bare prototype boards available with these units to dream up what you wish to do.