• on Test & Measurement
  • Published in issue 4/2011 on page 24
About the article

Pico C

Please welcome ATtiny & The Low Picofarads

Pico C

Even upmarket digital multimeters boasting a built-in capacitance meter are useless if you want to check out tiny capacitances like 2.7 pF or 5.6 pF. Usually, you’re tied to a lowest measuring range of 2000 pF, which is a good laugh to RF designers and radio amateurs. Although at 3.5 digits the DMM’s resolution is 1 pF, any measurement below 200 pF or so will produce coarse if not ridiculous results. Pico C does a far better job. Beating many DMMs hands down, this little instrument easily measures capacitances down to fractions of a picofarad.

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Gerber file

CAM/CAD data for the PCB referred to in this article is available as a Gerber file. Elektor GREEN and GOLD members can exclusively download these files for free as part of their membership. Gerber files allow a PCB to be produced on an appropriate device available locally, or through an online PCB manufacturing service.

Elektor recommends its business partner Eurocircuits as the company of choice for its own prototypes and volume production in selected cases.

Extra info, Update


- range: <1 pF to 2000 pF (guaranteed); 2500 pF possible
- resolution: 0.1 pF
- readout: 2-line LCD
- low-cost, no SMD parts
- ATtiny2313 DIP20 microcontroller
- free source and hex code
- easy calibration with 1000pF 1% reference capacitor
- microcontroller, board and kit available from Elektor


Please note

Kits are now supplied with controller # 110687-41 containing Pico C-Plus firmware. This is fully compatible with the existing circuit board.



R1 = 1MOhm 1%
R2 = 5.6Ohm
P1 = 10kOhm trimpot, horizontal
C1 = 10µF 63V, axial, lead spacing 2.5mm
C2,C3,C4 = 100nF 50V ceramic, lead spacing 0.2 in (5.08mm)
C5,C6 = 15pF 100V ceramic, lead spacing 0.2 in. (5.08mm)
C7 = 220pF 63V 1%, polystyrene, lead spacing 7.18mm, e.g. LCR Components # EXFS/HR 220PF +/- 1%
Optional: 1000pF 1% reference capacitor, polystyrene or polypropylene
D1 = 1N4004
IC1 = 7805
IC2 = TLC555 8-pin DIP, e.g. Texas Instruments TLC555CP
IC3 = ATtiny2313-20PU, programmed, Elektor Shop # 100823-41
K1 = 2-way PCB screw terminal block, lead spacing 5mm
K2 = 2-way pinheader and receptacle, lead spacing 0.1 in. (2.54mm)
JP1 = jumper, 0.1 in. (2.54mm)
S1 = pushbutton, SPNO, 6mm
X1 = 20MHz quartz crystal, CL=18pF, 50ppm, solder wires
LCD = DEM16217, 2x16 characters with backlight, e.g. Elektor # 030451-72
LCD connector = 16-way (14+2) SIL pinheader and socket, right angled, lead spacing 0.1 in. (2.54mm). See text for connection of DEM16217 LCD.
20-pin DIP socket for IC3
8-pin DIP socket for IC2
PCB, Elektor # 100823-1
Kit of parts, including Project Case, PCB, LCD and programmed microcontroller; Elektor # 100823-71
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