As an absolute "newbie" to Arduino and the IDE environment I trust that I do not upset anyone with my clarification question(s). I was actually in the Computer industry from 1963 so I am not a complete novice, just getting old and out of practice! Along the way I have owned Nascom 1 & 2 (z80 based) and played with most of the 8 bit processors (8080, 8052, 6800 etc.) I also serviced large mainframe systems and their peripherals (tapes, Drums, Discs Printers Comms Devices etc). I still keep my hand in from an Electronics point of view and actually have a number of operational Raspberry based projects (Security cameras, House service management, Media etc).
My reason for relating all the above is simply, in advance to apologise for any stupid question I may ask (old age is a terrible thing >:( !).
My problem:
I decided I needed to build myself a new Dual Bench power Supply and want to accurately measure the Output voltage and current consumed by whatever it is driving. I of course have a portable DVM , and even a Vintage AVO 8 but I thought it would be more elegant to actually have the measuring facility as Part of the unit. I could have simply bought 4 panel mounted LCD meters, butI thought it would be better and more challenging to use the Arduino based project using the LTC2400 ADC and a couple of MCUfriend 2.4" displays.
Now the problem - the sketch from David Prentice (circa 2013) uses a library UARTLCD.h which I can find no information on. My idea wsa that if I understood the methods used by that Library I would be able to edit the sketch to use the new Libraries based on MCUFRIEND and Adafruit_gfx. Having spent over a week not making any progress other that to get MCUFRIEND library to drive the tft's I have purchased when connected to an Arduiono R3.
One correspondent on the Forum suggests the way to do it is to use the serial version of the Sketch and edit it such that the print statements go to the TFT, I sadly haven't managed to do that.
If anyone can give me some guidane or help I would most appreciate it. I actually have built the Power Supply modules but dont want to cut any holes in the front panels until I have a better handle on the measuring bit. I apologise for the length of this question - it is my first attempt to use this forum.
LTC2400_ADC_UARTLCD_out.ino (5.09 KB)
LTC2400_ADC_Serial_out.ino (4.2 KB)
One correspondent on the Forum suggests ...
If there is an existing thread, it may be worth continuing there - or providing a link.
Do you have a block diagram of how you’re connecting everything up?
Seven digits is a lot of precision, unless it’s on the left of the DP.
Local reference etc, need to be an order of magnitude higher precision than the sample.
Sounds like a neat project.
Keep us informed!
P.s. Can you paste the code in-line with tags so everyone can see it. Thanks.
Hi Lastchance, thank you for the prompt response, I take note of your comments, but a couple of quick questions 1. how do I paste the code in line with Code tags? Doesn't attaching the SKETCH provide enough info? If you could clarify for me or maybe point to where about i can find guidance on this I would appreciate it. 2. On your precision comment the adc is a 24 bit device 3. There are couple of threads on this but i haven't managed to glean, with my limited knowledge, any answer to my problem. The manufacturer of the adc , ltc2400 has an excellent application note about utilising the ADD. My queries are really about how I integrate the ADS and the tft display and associated libraries into a module.
I still need to gather my thoughts on how to switch the input into the ADC from a voltage measurement to a current measurement , it's really the same except the current measurement is actually a much lower voltage measurement across a precision 0.2ohm shunt. I also obviously needt to display it in a different way on the tft.
Once again many thanks for your response and comment.
Regards,
Don
how do I paste the code in line with Code tags? Doesn't attaching the SKETCH provide enough info?
Select and COPY the code from your editor, then use the </> button in the toolbar.
In between the tags - PASTE your copied code.
-- the reason is that on mobile devices and even on desktops, no-one is interested ni launching the IDE or their text editor to 'take a look' at your code. If it's i the post - we can look at it directly, or SELECT & CUT it across to our own editor if needed.
The LTC2400 uses SPI to communicate - so as long as you aren't tying up those pins - the Arduino should have no problem talking to it. The (small) challenge I see immediately is getting a very stable Vreference to justify the 24-bit ADC resolution.
AD LTC2400 datasheet
My queries are really about how I integrate the ADC and the TFT display and associated libraries into a module.
Start with one piece at a time - I'd probably begin with a simple framework - using Serial.print() to verify basic operation and calculations.
Then add the ADC - and make sure it's doing what you expect.
Finally - add the TFT display - and you already know the other stuff is working - so you can gently move the displayed data across to the LCD.
thoughts on how to switch the input into the ADC from a voltage measurement to a current measurement , it's really the same except the current measurement is actually a much lower voltage measurement across a precision 0.2ohm shunt
.
You know what you need - so the next piece is to recognise that unless your current measurement is on the 0V side - you'll need a differential input because both points being sensed are above 0V/ground.
(If the shunt /is/ on the low-side - you can use the common 0V rail and measure the current being sunk by the PSU that way.)
Hi,
Welcome to the forum.
Please read the first post in any forum entitled how to use this forum.
http://forum.arduino.cc/index.php/topic,148850.0.html then look down to item #7 about how to post your code.
It will be formatted in a scrolling window that makes it easier to read.
Thanks.. Tom... 
Thank you for the responses and suggestions. Would you have any suggestions as to where I can find the library UARTLCD used in the original Tft SKETCH? Would it be within the forum protocol to approach David Prentice directly.
Would appreciate guidance.
Don
Hi Lastchance, your comments regarding the negative supply are spot on and yes I propose to measure the current flowing through the negative rail. Both the supplies are floating with no attachment to Ground. The reason for this is that I wish to be able to stack/connect them in series if I need a higher output. This means each has to have it's own Independent "input" transformer to the regulators and also a separate feed to each voltage measuring module. It also means they can be connected in parallel. It's more complex and a tad more expensive but I think the only simple solution. Ground reference is dependent on which is bonded to Earth
Regards,
Don
Hi,
Check that your voltmeter modules can be supplied by the supply it is measuring.
Most can't, they need their own floating supply.
Tom...