I've been doing some thinking about some projects that I want to start. It occurs to me that for many of them it would be nice to be able to do computer control of these devices. This would require that I be able to get analog inputs from the devices in question to a program running on my computer, and send analog outputs back to said device.

As far as how you go about doing that ...

It used to be that old RS-232 ports had some analog value to the pins, ect that could be called up with the appropriate drivers. However, my computer is a modern one and only has USB ports/ethernet, ect. I was looking for USB analog input devices, at which point I keep getting sucked into National Instruments website.

NI makes devices that look a lot like what I'm interested in. They're a bit pricey, but may be within my range.

But what really breaks the deal is that it appears I can't use it in a seperate application (such as the program I want to write) unless I buy their $4xxx professional software.

How do modern hobbyists do inputs/outputs to their computer without some sort of professional DAS device?

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Flight simulators for folks that fly radio control aircraft and helicopters use control boxes that are analog (and look just like the two stick radios that people use to fly radio control). At least I assume it is analog.

The one I have connects to a USB port.

So it has to be possible to get an analog signal into a USB port.

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Hmm. Nevermind. Maybe you can use the NI hardware without their professional software suite. They seem to give out the base NI-DAQmx drivers.

Anyone else work on a project, say robotics or computer driven control of something? What did you use?

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There are too many questions that need answered before a recommendation can me made, imo:

Is the analog voltage AC or DC and what is the voltage range?
How much precision is required?
Are the analog devices voltage or current loop (I assume voltage)?
Does it need to be isolated or common ground?
If you are going to control something, don't you need appropriate output?
..and if so there are more questions.

One final question - am I making it more complicated than it needs to be?

-V

Probably DC. Low voltage.
At this point I'd be happy to see a 8-bit int every half second or so.
Voltage
Eventually.

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Are they space- or astronomy-related, or did another general question land in space and astronomy Q&A?

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If you're good with circuits, just get some analog to digital converters, and digital to analog converters, and make a little control box to hold it all. Most IC's are ~$0.50 so this is a very cheap solution.

Serial to USB converter? That's what telescopes, focusers and autoguiders use to communicate with modern computers. I'm not exactly sure what you mean by "analog input": would it be ok if you could step across a range of values?

There's also the Lego Mindstorms boxes, though I don't know whether they could actually do what you want.

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If your PC has a parallel port, a simple device can be built that can supply six channels of analog input. Google PC voltmeter.

Also there are some products for direct analog to USB and they look pretty inexpensive - google USBee DX - software is free and can be used with Visual Basic.

Of course, all of these ideas are perfect for data acquisition for analog telescopic instruments such as homemade light meters, tracking devices, etc.

EDIT: never mind the USBee - too expensive - I might find some more tomorrow.

EDIT again: http://search.ebay.co.uk/_W0QQfgtpZ1...assZmatthijsfh - its in the UK - price in pounds - same device: http://home.planet.nl/~m.f.hajer/scope2k4/hardware.html

Don't bother with NI... just... don't.
*shudders*
Guess what I'm working with right now...

There are RS232-USB converters, though I don't think they help with your needs for analog.
An A/D converter in acceptable precision shouldn't be so difficult to solder, though...?

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Yeah, this is more of a general question. Sorry about misplacing the thread.

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How about this? Octopus USB. 8 analog inputs, 0-5V it seems.

It's somewhat ambiguous, but it seems the microcontroller may come unprogrammed currently. So you would additionally need an AVR programmer to load the provided firmware.

And if you're not that good with them, get converters with the I²C interface and google for "i2c bit-banging" to control them, fewer wires to keep track of.

Edit to add: Thanks, you got me triggered so I ended up looking for stuff for my own projects at Maxim¹ when I noticed they have free samples of many of their chips which would be ideal for me as I don't need more than two anyway.

1) I am not affiliated with them and is providing the link because it look like it may just be possible to get something for free there.

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And the "driving on the freeway on a scooter" analogy still holds true because the pilots are sitting in 7 to 30 ton aircraft o' doom and you are running around them in your very own Meatbody, Mark I. Beep, beep.
Trying to make sense of computers, The Error Log.