1 to 5 volt output from the propeller ?

JMLStamp2p

Good evening,
Is it possible to output 1 to 5 volts using a propeller output pin and a few external componets ? If so does anyone have a diagram or an object written ?

Lethal Python

You could create a R/2R ladder DAC

Are you asking if you can do that with 1 ouput pin? You could connect 2 pins to a serial in parallel out register

...but i haven't hands on experience with DAC yet

Mike Green

You can get a voltage between 0 and 3V using just the Propeller, a resistor, and a capacitor. Read the AN001 Counters Application Note that you can download from the Propeller Downloads web page. This can be run through an op-amp (which you'd want to do anyway) and, if you run the op-amp off a 5V or greater power supply, you can get your 1 to 5V signal.

Ariba

You can use a R-C combination for a simple DAC, which outputs 0...3.3V. And then a Operational Amplifier (OPAMP) with a Gain of 1.5 to amplify it to 0...5V. See the attached picture for a possible circuit.
You can for example use 1/2 LM358 for the OPAMP, but there are thousend others...
If you use a Rail-to-Rail-Output OPAMP like the TS922 the supply voltage of the OPAMP can also be 5V.

For such a R-C DAC no additional Cog is necessary, a Counter in Duty-Mode does the job:

CON
  DACpin  = 0               'Pin number

PUB
  ctra := %00110<<26 | DACpin
  dira[noparse][[/noparse]DACpin] := 1

'  frqa := $0666_0000        '~1V
  frqa := $8000_0000        '~2.5V
'  frqa := $FFF0_0000        '~5V

  repeat

(this code is not tested)

Andy

Rayman

A digital pot might work too...

StefanL38

hello JMLStamp2,

one simple way to create an analog voltage is to use a DAC-Chip.
To create a voltage-range from 1.0V to 5.0V you simply limit the digitalvalue-range
that it starts not at value zero but with the value that relates to 1.0V.

If you can effort 8 IO-PINs of the propeller you could use an 8 bit DAC with parallelinput.

Then the driverobject would be simply to set these 8 IO-PINs to a bytevalue.

CHIP-examples for parallel input DAC08

there is also one for I2C-interface PCF8591. Here you would have to use
the I2C-object and send the right adress- and valuebytes

best regards

Stefan

JMLStamp2p

Thanks guys,
I will check it out.
JMLStamp2p

Rayman

If you only needed to cover the range 1.7 to 5V, you might be able to use a couple diodes to upshift the DAC voltage...

JMLStamp2p

Thanks Rayman, I will be doing some reading for the next couple of days. I may yell back at you guys if I have any questions.

Regards,
JMLStamp2p