Uni-trend meter add on over RF  - Page 1
Forum section: electronics / projects

author: Steve44
author_rank: Newbie
timestamp: August 16, 2014, 04:45:59 pm
content: Hi all I’m new here even though I’ve been reading post’s and watching the videos on here and thought I’d start to share a little project that I’ve started and looking for feedback or where improvements could be made.I’ve embarked on a new gizmo project an add on for the uni-trend 70UT70B multi-meter, I got the idea while working out on site where I need to remotely see a voltage reading of the multi-meter which could be up to 100 feet away and rather than use extra-long wires or an extra body to shout out the reading while I pressed the button and I thought why not have ago at making it wireless using RF modules, So I set about doing some searching on the net found the data sheet for the chip used (ES51962 from Cyrustek) and read it to get an understanding of the data been transmitted.I wrote some code to see if I could decode the data by sending it to a Picmicro then back to the PC but found out it was not as simple has I thought, But after spending some time I found out that I did not enable the -10V on the serial cable as the computer does when you connect it to the software that came with it, I got it working and sending the data to PC from the Picmicro which was receiving it from the meter so I then set about adapting the TX/RX code which I’ve used in other projects to receive the data from the meter then send it over to the RX unit and this displayed the data as to what the meter was reading. Ran some initial tests out on site and it worked great, Over the last couple of months I’ve been adding more code so that you can use all the functionality of the meter over RF. This is now completed and carried out a lot of debugging and testing and it’s all now working 100% on every range, even though I only wanted DC voltage reading but thought if the jobs worth doing then do it right ?, It still may need a few tweaks here and there(how the data is displayed) and tidying the code up.Attached are some photo’s of my test boards in action and the schematics. Both TX&RX units use a PIC16F883 (not fully set in stone yet) 433MHZ RF modules 2X8 LCD and RS232 for TX unit and a MC33063 for the power supply. The MC33063 draws 2.3mA with no load and the TX unit draws in total 23milli-amps while transmitting, The RX unit with draws 83milli-amps while receiving and 100milli-amps with the buzzer is active, This could be possible reduced if I turn off the back light but then thought how often would I need to use the buzzer remotely.The schematics are drawn but not laid out the PCB’S yet has I’m unsure which is the best way to complete them, I’m thinking it may be better to combined the 2 together so that the same PCB can be used as a TX or RX unit save having 2 PCB’S made which will make it cheaper.Hopefully this is where you guys come and give input if the design could be improved like to be able to draw less current so it could be run from a 9V battery or 12V battery of some sort better way of the power supply design. I’m yet to select the case for them and this is another reason why the delay in the PCB’S. I have to use any 16F series picmicro because this works best with my RF code but the 18pin does not have enough memory for the RX unit routines, I have considered using 14pin pic for the TX and 28pin pic for TX but like the idea of 1 PCB.Hopefully you will find it interesting and may find a use for it, I’ve also added code that you can still use the PC and software that came with the meter over RF so you don’t have to have the PC close if you need to log data, I’m also considering adding a standalone data logger where you can store the values onto an SD card if you can’t send data to PC(like an application I have where I don’t really want to have a laptop in the workshop where it could get damaged.For the power supply part I’ve thought I’d run it of a PB9 battery or 6 x 1.2V 2000Ma minh batteries but not sure how long the PB9 battery would last on both units. Again your input would be grateful has many input ideas always comes up the best.So this sort of an on going project and thought it would be pointless in uploading the code until the design is finalized and near completion and save clogging up the thread with every minor update but willing to share HEX file if people are interested in it, I’ve only got the UT70B meter at the moment and I should be looking at getting the UT61E and UT71D meters and see if they work on this unit has I’m not sure if they send the data out in the same format but if someone who as a UT61E meter and willing to have at building one and doing some testing then let me know, I might be able to re-compile the code to work with other 16F series you may have lying around.Hopefully the images will be ok

author: Steve44
author_rank: Newbie
timestamp: August 17, 2014, 05:11:46 pm
content: I have been doing some more playing and found out that I can fit the code into 16F628A/16F684A yet to test to see how it works,I've also been and got a UT60E meter today but found out it uses a different chip (FS9721-LP3) which gives out a different format, I need to study the data sheet and get a better understanding how it works and try to figure out how to decode it and convert it to display the real data from the 14bytes of data.I've found this page with info but this is for the data logger which works with this meter.http://www.hw2sw.com/2012/09/26/designing-sw-for-mastech-ms8229/#more-4928Will have to read it and try to take it in and work out how to do it, Had a quick read through it and it's mushed up my head will have to clear it and try again.Hopefully at the end of this I will be able to use the same hardware and just the software change for each type of meter, My thinking that this could be used for the MASTECH MS8229 meter as this uses the same chip, Need to find out about what chip is in the UT61E and UT71D as it looks a nice meterwill keep you posted on any updates

author: Steve44
author_rank: Newbie
timestamp: August 29, 2014, 10:25:54 pm
content: Back again, I've carried out most of the coding and 90% working over RF, Still got a few issues that's I'm working on where some of the range mode's do not change cured most of them, The strange thing is that it all works if I put the meter straight into my Dev board so I know its to do with the data been streamed, Range is good and stable.Here is a quick video if anyone is interested, Only my second attempt at doing a video for youtube,Hopefully some one will find it interestinghttp://youtu.be/uIE4PAr2JRA