SirNickity
Member
Well, I guess there's always room for one more project... I've caught the 51x bug and have started planning my entry into said territory.
First items on the list: A few API-312s and a couple 1176-Ds. I'm picking these because they're easy designs. I'm not so worried about the build difficulty, but I have it in mind to customize them with the exact options I want -- so, no off-the-shelf kits for me. This implies a few iterations of the design phase, and so the first order of business will be a power supply that is suitable for testing purposes.
To that end, I'm looking at putting together a small test harness, with the EDAC port backplane and XLR/TRS I/O for two cards (in order to handle builds with 2U width or stereo links). The PSU rails will be limited to 150mA (16/24V) and 50mA (48V), with switchable current limiting at lower levels (e.g., 10, 25, 50, 100mA) for smoke testing, and a simple LED display of current consumed for a quick heads-up of what's going on.
Attached is a high level block diagram of what I have in mind. The TI LM5002 is a configurable switching regulator IC capable of 0.5A peak at up to 75V. The Linear Tech LT3471 is a dual-channel buck/boost/inverter that is good for +/-40V at a peak of 1.3A. Both should be able to provide more than enough current to downstream linear regulators for the positive (LT channel A boost to ~25 or 26V), negative (LT channel B inverting to -25V) and phantom (TI boosting to ~50V) rails. This makes is super easy to power the whole deal with a typical (though reasonably stout) wall wart of 12V or 20V (laptop) DC output.
The linear regulators will be designed around a P-MOSFET pass transistor, with a few op-amps in the feedback loop providing a constant voltage control scheme up to the selected current limit, and then constant current thereafter. Current consumption will be displayed by a simple resistor ladder + comparators driving some LEDs. I'm resisting the urge to drop in an ATtiny and reduce the parts count by a third, figuring some analog design might be nice for a change.
OK, that's all for now. Schemos and such to follow. (Only get to post one file at a time.)
First items on the list: A few API-312s and a couple 1176-Ds. I'm picking these because they're easy designs. I'm not so worried about the build difficulty, but I have it in mind to customize them with the exact options I want -- so, no off-the-shelf kits for me. This implies a few iterations of the design phase, and so the first order of business will be a power supply that is suitable for testing purposes.
To that end, I'm looking at putting together a small test harness, with the EDAC port backplane and XLR/TRS I/O for two cards (in order to handle builds with 2U width or stereo links). The PSU rails will be limited to 150mA (16/24V) and 50mA (48V), with switchable current limiting at lower levels (e.g., 10, 25, 50, 100mA) for smoke testing, and a simple LED display of current consumed for a quick heads-up of what's going on.
Attached is a high level block diagram of what I have in mind. The TI LM5002 is a configurable switching regulator IC capable of 0.5A peak at up to 75V. The Linear Tech LT3471 is a dual-channel buck/boost/inverter that is good for +/-40V at a peak of 1.3A. Both should be able to provide more than enough current to downstream linear regulators for the positive (LT channel A boost to ~25 or 26V), negative (LT channel B inverting to -25V) and phantom (TI boosting to ~50V) rails. This makes is super easy to power the whole deal with a typical (though reasonably stout) wall wart of 12V or 20V (laptop) DC output.
The linear regulators will be designed around a P-MOSFET pass transistor, with a few op-amps in the feedback loop providing a constant voltage control scheme up to the selected current limit, and then constant current thereafter. Current consumption will be displayed by a simple resistor ladder + comparators driving some LEDs. I'm resisting the urge to drop in an ATtiny and reduce the parts count by a third, figuring some analog design might be nice for a change.
OK, that's all for now. Schemos and such to follow. (Only get to post one file at a time.)