When choosing your network resistors for an R2R ladder, remember that the input impedance is always R, and this R vs the 30.1K series resistor in the module sets the minimum and maxim adjustment voltages. 1K is a good value to use for R since you can drive the voltage from 5V to 199V with a 5V GPIO rail and 2R=2K=2.5mA is well within the capability of most GPIOs. The part linked below with a 10K R would allow adjustment from 37V to 188V at 1/10 the processor current as a 1K network.
The next choice is how many GPIOs do you want to use, where the granularity is simply Span/(2^N): A 1K R2R network and 6 GPIOs gives you 3volts/step from 5V to 199V. On Tuesday, September 9, 2014 11:43:50 AM UTC-7, taylorjpt wrote: > > You can also build your own DAC with an R2R network controlled by GPIOs > that will give you a linear Radj = Vout voltage vs binary code. You can > buy R2R ladders off the shelf: > http://www.digikey.com/product-detail/en/4610X-R2R-103LF/4610X-R2R-103LF-ND/3787967 > > jt > > -- You received this message because you are subscribed to the Google Groups "neonixie-l" group. To unsubscribe from this group and stop receiving emails from it, send an email to [email protected]. To post to this group, send an email to [email protected]. To view this discussion on the web, visit https://groups.google.com/d/msgid/neonixie-l/c73fc9d3-6d7b-451c-8d84-8bb97542ca14%40googlegroups.com. For more options, visit https://groups.google.com/d/optout.
