Category Archives: power supply

Open heart surgery

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OK, maybe not as dramatic, but it was just as vital.

With my final project deadline extended a week, I took a couple days of downtime to catch up on sleep. The all-nighters were adding up. Now I’m back and making some minor changes and a few fixes. Hopefully the thing will drive in reverse without catching on fire. If you don’t hear from me, send help.

Firmware for the not has been fleshed out and I’m looking forward to getting it coded. The loop is simple, checking the status of each input and setting a flag. That flag is passed to the three output functions, which run after the input stage. One exception is the turnaround() function, which is called by an interrupt on the whisker pin. Some output functions call themselves to complete a series of drive commands, for instance. This keeps things simple.

More to come.

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2015-04-23 · 20:05

All together now

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2015-04-20 · 21:18

Late night testing

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2015-04-20 · 01:30

Power supply board

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Power supply board for my two wheeled robot. 5 and 3.3V provided by TI LDO regulators at 3A each, and fused vbatt for the motors. PPTC rated 3A IH at 12V. Protection from over voltage condition (important when combining motors and MCUs) using crowbar circuits. Divider and space reserved for a tiny85 to monitor battery voltage.

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Filed under analog, Battery power, edX, ICs, power supply, regulators, Soldering

Crowbar circuit for over-voltage protection

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Over-voltage protection for each rail of my project’s power supply in the form of a thyristor (silicon controlled rectifier or SCR) based crowbar circuit. The Zener breakdown voltage determines the cut off and trips the gate of the SCR, causing a short condition. The short is then handled by a fuse, protecting sensitive devices. A threshold of about 1V for the Zener diodes (4.3V for the 3.3V rail & 6.2V for the 5V rail) was selected to allow for overhead in case of transient spikes.

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2015-04-02 · 18:10