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projects:tek222bat [2017-11-04 06:38] robert |
projects:tek222bat [2020-05-31 11:32] (current) robert [Tektronix 222 Battery Pack] |
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===== Tektronix 222 Battery Pack ===== | ===== Tektronix 222 Battery Pack ===== | ||
- | For those of you interested in a multimedia audio-visual experience, there is a little overview video of the battery pack of youtube [[https://youtu.be/LJ2VS3aohV0|here]]. | + | For those of you interested in a multimedia audio-visual experience, there is a little overview video of the battery pack on youtube [[https://youtu.be/LJ2VS3aohV0|here]]. |
+ | |||
+ | If you would like to buy a ready-made replacement battery unit based on this design, N0DY Electronics is building and selling them [[https://www.n0dy.com/product/tekcharger/|here]]. | ||
==== Introduction ==== | ==== Introduction ==== | ||
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==== Overview ==== | ==== Overview ==== | ||
- | Starting out, I new that I had to (or wanted to) build a circuit that wraps around one or more lithium cells and makes them behave like the original 8V SLA battery as far as the scope is concerned. The way I chose to achieve this is shown in the following diagram: | + | Starting out, I knew that I had to (or wanted to) build a circuit that wraps around one or more lithium cells and makes them behave like the original 8V SLA battery as far as the scope is concerned. The way I chose to achieve this is shown in the following diagram: |
{{ :projects:scope-bat.png?direct&400 |}} | {{ :projects:scope-bat.png?direct&400 |}} | ||
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* PCB Gerbers {{:projects:scope-bat1.zip?linkonly}} | * PCB Gerbers {{:projects:scope-bat1.zip?linkonly}} | ||
* Schematic and PCB layout (DipTrace 3.1) {{:projects:scope-bat1-design.zip?linkonly}} | * Schematic and PCB layout (DipTrace 3.1) {{:projects:scope-bat1-design.zip?linkonly}} | ||
+ | * DXF files for acrylic case parts {{:projects:bat-acrylic.dxf?linkonly}} | ||
- | The above files are for Revision 1 of the board, which I have not yet built and tested. However, the only changes from Revision 0 are fixes for a few mistakes so hopefully it should work without any issues. | + | The above files are for Revision 1 of the board, which has been built a number of times and proved to be robust. |
- | + | ||
- | If for any reason you'd like the Revision 0 design files you can find them here: | + | |
- | * Schematic PDF {{:projects:scope-bat-sch0.pdf?linkonly}} | + | |
- | * Bill of Materials {{:projects:scope-bat-bom.csv?linkonly}} | + | |
- | * PCB Gerbers {{:projects:scope-bat-gerbers0.zip?linkonly}} | + | |
- | * Schematic and PCB layout (DipTrace 2.9) {{:projects:scope-bat-design0.zip?linkonly}} | + | |
- | + | ||
- | If you decide to build the circuit from the Revision 0 board / schematic, you need to apply the following fixes: | + | |
- | * Add a 1MΩ pull-up resistor on OUTA (pin 1) to Vs (pin 5) of the LT6700. | + | |
- | * Add a 4.7µF ceramic capacitor in parallel with the decoupling capacitor of the LT6700. | + | |
- | * Add a 10MΩ feedback resistor between OUTA (pin 1) and INA, INB (pins 3 and 4) of the LT6700. This increases the hysteresis voltage. (optional) | + | |
- | * Add a 1µF ceramic capacitor in parallel with each of the electrolytic capacitors. | + | |
{{ :projects:bat-switcher-top.jpg?direct&400 |}} | {{ :projects:bat-switcher-top.jpg?direct&400 |}} | ||
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The datasheet does mention that the reference is sensitive to noise, but I didn't expect it to have that kind of effect. Adding a 4.7μF decoupling cap on the comparator in parallel to the existing 100nF solved that issue. If I were to re-spin the board, I'd probably add an RC filter on the supply line, just to be on the safe side. | The datasheet does mention that the reference is sensitive to noise, but I didn't expect it to have that kind of effect. Adding a 4.7μF decoupling cap on the comparator in parallel to the existing 100nF solved that issue. If I were to re-spin the board, I'd probably add an RC filter on the supply line, just to be on the safe side. | ||
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