Article

Beep

The sounding logic probe/tester

Even if you have an upmarket logic analyzer and are completely at ease with its operation, you are unlikely to use it to debug simple circuits like Arduino and Raspberry Pi add-on boards. That’s where Beep comes in.

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Materials

www.elektor.com/140410

https://github.com/ElektorLabs/PreferredParts

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Components

The BOM (Bill of Materials) is the technically exhaustive listing of parts and other hardware items used to produce the working and tested prototype of any Elektor Labs project. The BOM file contains deeper information than the Component List published for the same project in Elektor Magazine. If required the BOM gets updated directly by our lab engineers. As a reader, you can download the list here.
Want to learn more about our BOM list? Read the BOM list article for extra information.

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Component list

Component List
Resistors
Default: 5%, 0.25 W
R1, R3 = 2.2MOhm
R2 = 1MOhm
R4, R6 = 10kOhm
R5 = 1kOhm
R7 = 0Ohm (alternatively, wire piece)
Capacitors
Default: 0.2” pitch
C1,C2,C3 = 4.7µF 50V (2mm pitch)
C4 = 82pF
C5 = 470nF
C6 = 330nF
C7 = 100nF
Semiconductors
IC1 = HEF4040BP (or equivalent)
IC2 = CD4050BE (or equivalent)
IC3 = HEF4093BP (or equivalent)
Miscellaneous
SW1 = slide switch, 2-pole 3-position (RS 702-3568 or similar)
BZ1 = buzzer 12mm diam.
JP1, JP2 = 2-pin pinheader
2 pcs DIP-16 IC socket (IC1 and IC2)
1 pc DIP-14 IC socket (IC3)
Case, Hammond 1593D
PCB, Elektor Store # 140410-1

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Discussion (3 comments)

VINCENT CAPIZZO 4 years ago

The '4040 counter has a Schmitt trigger clock input, but the clock pin doesn't have a DC path to a logic high or low. Is this OK?

Vince Capizzo

ElektorLabs 4 years ago

Yes. The role of IC1 ('4040) is to divide the input frequency down to something audible, so its input is supposed to be an alternating signal. C4 only passes the edges of that signal, both rising and falling, which averages to 0. When there is no alternating signal, IC1 just stops counting. A pull-down resistor could be added if you like, but that means an extra resistor. You could argue that a diode is needed to protect IC1 against negative pulses, but they are very short, so we save a diode too.

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VINCENT CAPIZZO 4 years ago

Thanks for the explanation.

Normally a "floating" CMOS input is not a good thing, but in this case it appears to be OK. The data sheet for a MC14040B states that there is "No Limit" on the clock rise and fall time. In that case it all makes sense, and yes, save a resistor!

Thank you again.

Vince Capizzo

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