Eval¶

Overall design¶

• 4 x red+green LEDs for condition
• Restart button
• Iterate over the ADC channels and get Voltage level
• draw 100mA
• Die Kabel haben AWG28, 212.9 Ohm/km, 1.4 A nach erde, 0.23 A versorgung
• 0,2129 Ohm/m; 1,0645 Ohm/5m; 2,129 Ohm/10m;
• https://de.wikipedia.org/wiki/E-Reihe#/media/Datei:E12_values_graph.svg
• Buzzer would be nice for indication; durchklingeln
• PWM Output
• Pinsocket connected to wires to measure resistance/Voltage directly

Calculations I¶

U2=((U*R2)/R_GES)

U
R*I

5V/0,1A= 50 Ohm
5V*0,1A= 0,5 W

5V/0,5A= 10 Ohm

RGes = R1+R2 = 50

3V=(5*R2)/50
R2 = (3*50)/5 = 30 -> 27
R1 = 22
RGES = 49

U2 = 5*27/49 = 2,755102

theoretically an device that draws 0,1A and 5m:
U2=((5*50)/ (50+1,0645) ) = 4,8957691; that should work

theoretically an device that draws 0,5A and 10m:
U2 = ( (5*10) / (10+2,129) ) = 4,1223514 V

Calculations II¶

• Ein Kabel >= 10m soll durchfallen. Koennen trotzdem groessere Wiederstaende verwendet werden?

Keyfeatures¶

• Cable checker
• Buzzer Durchgangspruefer
• PWM Output

MCU¶

• stm32f051c4
  • I have 17;
  • 16 ADC channels
• STM32G030C8T6
  • nearly same specs but smaller footprint; LQFP 48
  • 2,68€ inc. Mwst.