Wireless MultiMeter

Original documentation from:

TechDesign Electronics

original idea and concept by Dany Bavin.




This project comes as a KIT. It includes these components:

  • Low-cost DMM (digital multimeter) M830D
  • TX (transmitter) circuit and  wireless module TX-433. These are mounted within the DMM housing.
  • RX (receiving) circuit with a  wireless module RX-433, LCD and piezo buzzer.

The general idea is to read all LCD data from a cheap DMM (directly from its main chip.) This data is sent and received by wireless modules, read by the RX circuit and then displayed again. Sounds pretty easy, not?

Here are the technical specifications:

  • Low power operation (8-10 mA @9V) with PIC 18F452 (TX) and 18F2550 (RX) microcontrollers running at 4 MhZ.
  • Sampling rate: around 3 samples/sec.
  • Max. distance between the RX and TX circuits: 30m indoors and 100m outdoors.
  • Software is 100% upgradable with a simple bootloader.
  • Low power LED blinks when sending / receiving data.
  • TX circuit: PCB Dimensions: 30 x 31 mm or 1"18 x 1"22, weight: 8 grams.
  • RX circuit: LCD contrast adjustable by user.
  • RX circuit: PCB Dimensions: 40 x 41 mm or 1"57 x 1"61, weight: 10 grams.


  Hex files available. Last update: June 1, 2006.


Main Connections:

RX circuit diagram (top view)

Header pinouts *

JP1  Nokia 3310 LCD  


RS232 interface   JP3  RX module, supply, I/O
1 VDD, +5V   4 TX   1  +9V input from battery
2 SCLK   3 GND   2  input from RX-433 module
3 SDA   2 RX   3 NC (no connect.)
4 D/C   1 +5V   4 GND (to battery and RX-433)
5 CS         5 LCD contrast adjust input
6 GND         6 +5V output (to RX-433)
7 Vout            
8 RES            
* Note: pin 1 is marked by a  red arrow in the diagram


TX circuit diagram (top view)

Header pinouts *

JP1  to TX-433 module   JP2  RS232   JP3  LCD inputs   JP5  LCD inputs
1 +V   1 +V   1 +V   8 A2
2 TX_out   2 RX   2 G2   7 B2
3 GND   3 GND   3 C3   6 C2
      4 TX   4 A3   5 D2
            5 G3   4 E1
            6 COM (GND)   3 G1
            7 NC, no connect.   2 F1
            8 BP, backpane   1 A1


JP6 LCD inputs   JP7 LCD inputs   JP8 LCD inputs
8 Buzzer in   1 B1   1 B3
7 Lobat in   2 C1   2 D3
6 dp1   3 D1   3 E2
5 dp2         4 F2
4 POL            
3 AB4            
2 E3            
1 F3            
* Note: pin 1 is marked by a  red arrow in the diagram

DMM LCD connections

DMM M830D chip pictures DMM M830D chip pinout (top view)

RS232 interface: JP2 provides the interface to connect to your COM port and hyper terminal. Also used for bootloading (module software update.) Check under the download section below for the latest version. Bootloading of the HEX-file can be done with Tiny Bootloader.

RX circuit, LCD contrast Adjust: Connect pin 5, JP3 to +5V before powering up. Release when the desired the contrast is reached.

Downloads: right-click & save as

  WARNING: may not be duplicated for any commercial use whatsoever without explicit consent from the author (c) Michel Bavin, TechDesign Electronics.


 TX circuit HEX: 025tx_v10.hex for 18f452 - May 31, 2006.

 RX circuit HEX: 025rx_v009.hex for 18f2550 - June 1, 2006.

Both can be bootloaded with  Tiny PIC bootloader through the RS232 port (JP2)


 TX & RX circuit schematics, pcb layouts and CCS C Source Code: not released, but you can buy a license on our Products page.


Info & datasheet:

Graphic LCD module type LPH7779 (NOKIA 3310 LCD) 48*84 pixels and its integrated controller PCD8544.


TX circuit (top view)

RX circuit (top view) DMM (back cover removed) RX circuit (working)

WMM KIT 1 contents: picture WMM KIT 1 contents: description
  1. DMM M830D
  2. Nokia 3310 LCD
  3. RX circuit
  4. RX-433 module
  5. SIL contacts
  6. Piezo buzzer
  7. 9V battery clip
  8. TX circuit
  9. TX-433 module
  10. Flatcable


 Blue= TX (DMM, TX circuit and module)

 Black= RX (RX circuit and module, LCD, Buzzer)


The PIC code was made with the PCWH CCS compiler ($425,-); you can install Microchip's MPLAB IDE (click on the link and you can get it for free) with it to get things running smoothly.

Bootloading of the modules is done with the excellent Tiny PIC bootloader, through RS232 (JP2).

Eagle 4.11e was used for the schematic & PCB layout. 


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