• on Test & Measurement
  • Published in issue 1/2009 on page 40
About the article

Meeting Cost Timer

Hidden costs become totally transparent!

Meeting Cost Timer
Longwinded discussions are costing commerce millions. Our meeting cost timer reveals the true cost of ‘free speech’ at business gatherings. The large seven-segment display lets you watch your money running away, whilst a single turn-and-push control switch makes operation of this attractive timer child’s play.
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Gerber file

CAM/CAD data for the PCB referred to in this article is available as a Gerber file. Elektor 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
Quick project specs
- 70 mm tall 7-segment displays
- Maximum total displayed: 9999.99
- Single switch operation using rotary encoder with press-button function
- Connections and operating control can be mounted on either the right or left-hand side of the PCB
- Controller: ATMega168-20PU
- ISP adapter for programming
- Power supply using 12 V / 800 mA mains adapter
(all 0.25W, 5%)
R1 = 220O
R2-R8 = 150O
R9 = 10kO

C1 = 330nF, ceramic, lead pitch 5mm
C2 = 10µF 16V
C3-C8 = 100nF, ceramic, lead pitch 5mm

D1 = 1N5817 (Schottky diode, 1A)
IC1 = LM7805 (TO220 case)
IC2,IC3 = L293DNE, DIP16 case (Farnell # 1470423)
IC4 = ULN2803A, DIP18 case (Farnell # 1047761)
IC5 = 74HCT238, DIP16 case (Farnell # 382231)
IC6 = ATmega168-20PU, DIP28 case, programmed, Elektor SHOP # 080396-41
IC7 = PCF8583P, DIP8 case (Farnell # 403908)
LD1-LD6 = SA23-12SRWA (Kingbright), 7-segment LED display, red, common anode (Farnell # 1168639)

X1,X2 = 32768 Hz quartz crystal, cylindrical housing 3x8mm
K1,K2 (optional) = mains adapter connectors for PCB mounting
K3 = 6-way DIL pinheader, lead pitch 2.54 mm (Farnell # 1096984)
S1,S2 (optional) = EC11B15242 (Alps), rotary encoder for front panel mounting, 11mm (Farnell #1191733)
PCB no. 080396-1 from the Elektor SHOP
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