en:tech:tonohmmeter
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| en:tech:tonohmmeter [2022/09/26 09:00] – [Links] bullar | en:tech:tonohmmeter [2026/08/12 14:01] (current) – claude | ||
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| ==== Motivation ==== | ==== Motivation ==== | ||
| - | {{: tech: tonohmmeter.jpg? | + | {{ :media:tech: |
| Everyone knows the problem that circuits or wiring do not work due to short circuits or interruptions. The domestic multimeter offers a continuity tester that acoustically reveals a low-resistance connection. It only becomes difficult if the location of the short circuit does not reveal itself immediately. A tonohmmeter can be used for such cases. This means that the measured resistance is mapped to the associated pitch. The smaller the resistance, the higher the tone. If the measuring range is sensitive enough, you can get closer to the cause. | Everyone knows the problem that circuits or wiring do not work due to short circuits or interruptions. The domestic multimeter offers a continuity tester that acoustically reveals a low-resistance connection. It only becomes difficult if the location of the short circuit does not reveal itself immediately. A tonohmmeter can be used for such cases. This means that the measured resistance is mapped to the associated pitch. The smaller the resistance, the higher the tone. If the measuring range is sensitive enough, you can get closer to the cause. | ||
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| ==== Measuring principle ==== | ==== Measuring principle ==== | ||
| - | {{: tech: hantek69_1.jpg? | + | {{ :media:tech: |
| The resistance is measured via the voltage drop. In order to be able to carry out measurements within circuits, a square-wave signal with approx. 340mV (the usual ESD structures of the ICs do not open) is released onto the unknown resistor. The resulting voltage drop is then amplified and rectified via OpAmps. The AVR does the AD conversion and audio output. | The resistance is measured via the voltage drop. In order to be able to carry out measurements within circuits, a square-wave signal with approx. 340mV (the usual ESD structures of the ICs do not open) is released onto the unknown resistor. The resulting voltage drop is then amplified and rectified via OpAmps. The AVR does the AD conversion and audio output. | ||
| ==== Hardware ==== | ==== Hardware ==== | ||
| - | {{: tech: schematic_tonohmmeter.png? | + | {{ :media:tech: |
| - | {{: tech: tonohmmeter_offen.jpg? | + | {{ :media:tech: |
| ==== Power supply ==== | ==== Power supply ==== | ||
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| The device is only operated via one key (U1). The hardware debouncing (C8 / R3 / R4) avoids the otherwise necessary software. The measuring range is displayed via three LEDs (LED2-4) and the sound output is performed by a small loudspeaker that is capacitively connected to the digital port. That is enough for simple tones. After all, we don't want to output MP3. | The device is only operated via one key (U1). The hardware debouncing (C8 / R3 / R4) avoids the otherwise necessary software. The measuring range is displayed via three LEDs (LED2-4) and the sound output is performed by a small loudspeaker that is capacitively connected to the digital port. That is enough for simple tones. After all, we don't want to output MP3. | ||
| ==== PCB ==== | ==== PCB ==== | ||
| - | {{: tech: tonohmmeter_pcb.png? | + | {{ :media:tech: |
| Since I liked the handheld housing from HAMMOND, it was difficult to find a LiPo that was the right size. Unfortunately I only found one for the front, so the board got a bit tight and is populated on both sides. At one end are the two jack sockets for the measuring strips and at the bottom the charging socket with charge indicator. The unused routing area is designed as a ground area. The AVD-ISP connection can be seen on the left, which enables us to do on-board programming. | Since I liked the handheld housing from HAMMOND, it was difficult to find a LiPo that was the right size. Unfortunately I only found one for the front, so the board got a bit tight and is populated on both sides. At one end are the two jack sockets for the measuring strips and at the bottom the charging socket with charge indicator. The unused routing area is designed as a ground area. The AVD-ISP connection can be seen on the left, which enables us to do on-board programming. | ||
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| ==== Downloads ==== | ==== Downloads ==== | ||
| - | * {{: tech: Tonohmmeter_v11.c.zip | Firmware Source Code}} in C | + | * {{ :media:tech:tonohmmeter: |
| - | * {{: tech: TonOhmMeter_HEX.zip | HEX files for fast programming}} | + | * {{ :media:tech:tonohmmeter: |
| - | * {{: tech: Tonohmmeter.pdf | drilling template front side}} | + | * {{ :media:tech:tonohmmeter: |
| - | * {{: tech: Tonohmmeter_bom.pdf | Equipment list (BOM)}} | + | * {{ :media:tech:tonohmmeter: |
| - | * {{: tech: TonOhmMeter_BOTTOM.pdf | assembly plan back side}} | + | * {{ :media:tech:tonohmmeter: |
| - | * {{: tech: TonOhmMeter_TOP.pdf | Assembly plan front side}} | + | * {{ :media:tech:tonohmmeter: |
| ==== Links ==== | ==== Links ==== | ||
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| ==== Donate ==== | ==== Donate ==== | ||
| - | If you line my articles feel to donate a cappuccino or so... | + | If you like my articles feel to donate a cappuccino or so... |
| < | < | ||
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