hello,
I would like to share my second DIY project with you,
My first Lipo project can be found at following link.
http://www.rcgroups.com/forums/showthread.php?t=1674209

I used a 433 MHz transmitter and receiver pair.
you can easily find these modules from e-bay or your famous elctronic market.

you can find the compiled hex codes and C codes who want to play with it.
also you will find my simulation file if you want to test without produce the device.

The transmitter circuit would be my verion1 circuit at above link, it use PIC12F675. I used software RS232 because I like to keep the device as small as I can make. You cand set your alarm level with a jumper on transmitter. In software I just preset them 3.3V and 3.5V.
The receiver circuit can be foun in attached file. It uses PIC 18F452, but you can use any PIC capable to drive LCD and have a RS232 interface.
at the init sequence the receiver trying to synchronize to the transmitter. If receiver could not receive enough successful packets from transmitter in a predefined interval. It will display error! on LCD. If successful packets received it will start to display cell1, cell2, cell3 and alarm set voltages sequentialy.
also receiver taking care about being in range or out of range.

I will be very hapy if you add your comments and bring your new ideas here.
regards,
Kemal

This is the final version for 3S1P pack
I've included all source code, PCB layout and circuit scematics of transmitter and receiver

hello kyildirim

You can develop programs like this device?

Hello fantasy1988,
that device, which already I have one of them also, possibly have auto cell discovery feature that I have not solve in software yet.
But I will continue to devolep my project in time.

Actually my receiver part is more informative than this one which showing cell voltages sequentially, mine is showing all cell voltages on the same screen.
I have added a photo of receiver prototype on breadboard in previous message.

If you put your ideas here, I will glad to help if I can.
regards,
Kemal

hi,thank you

You can help me write a program for PIC 16f628,or 16f88

the three LED display, 2 to 8 cell

Hobbyking 2-8S Cell Checker with Low Voltage Alarm (1 min 18 sec)

fantasy1988,
at the moment I have only time for my project
and also there are some software and hardware issues that I can't solve at the moment.
regards,

looks great
I'm planing to make one with AVR, with more telemetry options

what is the max range of the 433Mhz radio link?
what ant have you used

I am using very cheap Chinese product that I don't know the exact brand name.
I just attached the photo of transmitter and receiver that I am using
transmitter module is R433A
my receiver has no cyrstal, but have not see any side effect yet.

range is a combination of all components; quality of the RX and TX circuts
antenna on both RX and TX have big importance

I have'nt test more than 30m yet

more interesting thing that I discover; it is working between second floor and basement. as you migth know 2.4 wireless APs mostly are not working in this situation.

regards,
kemal

have you tired to put antenna

back then when i made my first project, i have used wire warp, but you got to
cut it to the right size

On transmitter I am using the spare wire on connector
On receiver I just wrap single core 17 cm copper wire.

below is the prototype receiver and final tranmitter connected to LiPo.

Originally Posted by kyildirim

On transmitter I am using the spare wire on connector
On receiver I just wrap single core 17 cm copper wire.

below is the prototype receiver and final tranmitter connected to LiPo.

Whilst approx 17cm is correct for the frequency in use (1/4 wave) if you have some means of measuring signal strength or the limits of range you can try adjusting the length, start long and cut bits off.

It may not improve but I have seen some significant improvements with a 433Mhz devices by tuning the antenna in this way.

Originally Posted by srnet

Whilst approx 17cm is correct for the frequency in use (1/4 wave) if you have some means of measuring signal strength or the limits of range you can try adjusting the length, start long and cut bits off.

It may not improve but I have seen some significant improvements with a 433Mhz devices by tuning the antenna in this way.

hello srnet,
I am not measuring the signal strength neither distance, actually I don't know how to do it.
I am basically measuring count of successful messages in a predefined interval
If the number of messages enough, I am assuming we are in range.

I will try the device this weekend, will provide the details.

Originally Posted by kyildirim

hello srnet,
I am not measuring the signal strength neither distance, actually I don't know how to do it.

You have a receiver, so de-sensitize it by cutting the antenna off, or very short.

Take the transmitter over to your local field, and starting some distance away from the transmitter (I doubt it would be more than 100m) approach the transmitter until you strat recieving data. You now have a benchmark.

Then start with a long antenna on the transmitter, and see what effect the varying lengths have on the distance at which reception just starts.

No fancy test gear is needed.

Originally Posted by srnet

You have a receiver, so de-sensitize it by cutting the antenna off, or very short.

Take the transmitter over to your local field, and starting some distance away from the transmitter (I doubt it would be more than 100m) approach the transmitter until you strat recieving data. You now have a benchmark.

If it will work in 100m that would be OK for me.
by the way, it is possible to replace with a long antenna cable but I am worry about the long cable on my TREX450, need more care than this one.

I have just tested the transmitter in an open area. It lost the signal reception after about 80m. May be it is possible to work over 100m range if I install a long antenna cable as srnet wrote above.