Here's a small size and low current draw voltmeter to use on development projects. Tack it into circuitry to keep an eye on a voltage without tying up a multimeter. Use the free Cosmic STM8 compiler and a low cost ST-LINK programmer to customize to your needs.

Kit contains board and LCD. LCD will need to be thru-hole soldered to board.

Features:

• Board dimensions 0.9 x 0.7 inches, 0.25 inches thick with LCD.
• Vin measurement range 0-33Vdc with installed 0603, 300k over 33k voltage divider. Customize as you wish.
• Supply voltage range 3-45Vdc into on board AP3735-33SA 3.3Vdc regulator. Meter will run down to about 2.0Vdc.
• Low supply current draw of about 700uA.
• 32.768kHz crystal on board for use with RTC or as a reference for frequency counter, etc.
• STM8L152C6T6 low power microcontroller.
• Example main.c program implements 0-33Vdc voltmeter using micro's internal Vref.

Through Hole Pad Functions (0.1" pitch):

• TIM1_CH1
• TIM1_ETR
• ADC1_IN7
• VIN through voltage divider to ADC1_IN7
• DAC_OUT
• TX
• RX
• SWIM
• RESET
• 3.3Vdc
• 3-45Vdc PWR to voltage regulator
• GND x 3

Micro will ship with example program installed, but software calibration may be needed due to component variations.

NOTE: Due to space constraints, there are no reverse polarity or other protections on the board... USE AT YOUR OWN RISK!