I'm trying to get going with an ADC but i just can't find what I'm after. I need a basic 8 bit one, nothing fancy, TTL as it'll be interfacing with a parallel port, any ideas on which models best? Stuff like the ICL7106's with in built 3.5 Digit Display Driver seem pretty easy to wire up (and cheap!), but have no 8 bit outputs. I've got an ADC084LCN in stock for some reason, I've found a datasheet but its not been much use in helping me wire up a simple circuit to measure between 0.00 and 2.00V(/1.99V). Any help or advice would be greatly appreciated.
Not that I normally going about reccomending other forums, but you may want to try posting or even just searching on here . (example of 1 result using analouge digital as the search criteria) http://www.electro-tech-online.com/viewtopic.php?t=4563&highlight=analouge+digital
Is this the datasheet you've got? http://www.ee.ualberta.ca/~verret/ee401/adc0801-5.pdf Seems to be quite a lot in that, prob too much... I can dig out my notes if that's no help, did some pretty basic stuff with A2D's last year.
Look on elecetronic parts places to see what they have in stock. Try to find somethign with an easy interface. If its over 8 bit, dont worry, just tie to the 8 MSBs. The rest are just better resolution. Only problem is that most ADCs have binary outputs, so if you plan to stick with glue logic, you'll then need use BCD converters and such. Of course, you already know my suggestion. Id use a analog multiplexor to measure 8 different sources on one ADC channel.
I looked at a document that was over 100 pages long, so thats much simpler, i found one circuit that might be off use in there, i'll try to wire it up when my new protoboard arrives. What kind of basic stuff did you do? All i'm after is being able to read a voltage between 0 and 2v and convert it to a binary number. Cheers for the help everyone.
Acrim, what place do you normally get parts from (online)? I can search through and find something and give tips. ADCs come in a thousand different flavors. I cuold find something fast enough for me in the states, but that wont help you much. Give me a place to start and I can take a look.
www.farnell.co.uk <- biggest but a crap site www.maplin.co.uk <- not a great range www.rapidelectronics.co.uk <-favorite supplier, but not a huge range www.rswww.co.uk <- a good balance. Are the main ones in no particular order.
From Rapid: Pg 542 National Semiconductors part ADC0804LCN. price: 2.60 It original use is to interface with a microcontroller. You have 3 inputs and one output control lines, with 8 data lines (8 bit conversion). I would use a 74XX373/573 DFF latch to latch the results using the output (INTR interupt) to latch the data. The datasheet here has a section which shows a 'free running' ADC circuit. Using glue logic and a decade counter, you can take the INTR output and correctly time the inputs. CS (chip select) can be tied to ground. An adequte delay using the INTR and a decade counter should be enough to time a proper RD enable starting a new conversion. This can give you a free running 8 bit ADC using only TTL ICs. It uses 5V supply as reference (although you can use external reference) to derive the 8 bit result. Im sure you already know that the 8 bit is a division from 5V that will need to be converted to a number. So, each bit will correspond to 5V/256 bits = 0.0195 volts. Converting the binary value into something that can be displayed is another search altogether.
my bad. actually was using an 8 bit counter and a D2A conv in the form of the MP7524 to produce an A2D All this just to produce a prototype digital weighing machine. Definitely did other work (although not practicaly) with A2D chips, which I think would probably be much quicker than the above. Although the above is very basic and so simple to understand so I can give you some circuit diags and explanations if you want? Found some stuff I did with the ADC0809 simmilar to what Hazer is suggesting. The 0809 looks a bit easier to control but maybe I'm just thick It also has 8 multiplexed inputs which is prob more than you need but hey.. you could upgrade I take it your using the parrallel port to control the process?
I'll check out your recoomendations some more The idea is as follows: Potential Divider Circuit to reduce divide to beween 0 and 2 -> ADC input -> 8 bit binary number output -> 8 input bits of parallel port -> vb program that displays number.
Probably a misguided thought, but have you tried using the A/Ds in your sound card? joystick http://www.epanorama.net/documents/joystick/index.html spectrum/high freq voltmeter http://www.relisoft.com/Freeware/freq.html misc ham http://www.ac6v.com/software.htm tons of scope programs and some might actually apply.. . would require calibration. beats writing controller code and buiding circuits from store bought ICs. Sorry if I misunderstood your application.
i just had about adc and dac at school so i made this curcuit. dont know if i was what you needed. The resistors are just for referance so the size doesnt matter. Use any type of op-amp. You dont get a true binary output, but some programming skills will manage it.
I have specific critera for this so i can't use the old soundcard input trick, although i am aware of it and will be trying ti sometime As for the op amp circuit, thats just going up in a bargraph form rather than a binary number form, this will have 0 to 8 numbers, the problem is i need to represent numbers 0 to 200. In a 8 bit number i wil be able to represent numbers from 0 to 225 and then place the decimal point accordingly. I'm trying to wire up the test circuit for the ADC i have in stock but am sort of a few capacitors so i'll have to wait a while before it gets done.
