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SRAD Altimeter #91
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SRAD Altimeter #91
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…er selector, 12V/3V3 current sense, swapped pyros to BATT/3V3 from BATT/5V in
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- Your labels for the programming pins are wrong. When only 2 pins are connecting we're using SWD not JTAG mode
- Why do you have boot0 selection and a reset jumper? IIRC we've never used either, and camera worked just fine without either.
- Why do you have an external oscillator? Again camera worked without it, the internal one is usually fine?
- Resize the LED resistors for 3.3V
- There are weird doubled up DNP resistors on the pololu sheet?
- You don't need to connect to the pololu addr pin, save yourself the hassle and 1x1 connector.
- Also you should inject 3.3V direct to VDD on the pololu not via VIN
- It would be nice to use the 4R resistor as a pyro current sense measurement for real, probably via a voltage divider of the low side into the STM?
- CANH/CANL test points are kinda silly cause there's a connector right there
- I'd move the main/drogue testpoints to the pyro sheet
- I'd also move the current sense testpoints to the power sheet
- The INA4180 is kinda hard to lay out, I'd suggest 2x INA2180, one on the power sheet and one on the main sheet
- The 5V LDO max input voltage is 12V, but lipos go to 12.6
- The 3.3V buck has a soft start time of 2ms which isnt enough to charge the capacitor given its 3A limit, so we're going to be overcurrenting it. I really think you should reduce the requirements on that capacitor to make it a more reasonable size, eg maybe you only need 20ms and the STM32 can handle going to 2V or something, idk. Otherwise you need a buck with configurable soft start.
- F1 has the wrong footprint, also are there smaller options? Its kinda big
- L1 schematic value should be the part number, not the size
- Same for C31
- The ferrite bead is 0603, choose an 0805 one?
- The SDMMC app note link is missing
- I glanced at it but pls try to configure all your pins in STM32cube and make sure its happy before ordering
- Like Zach mentioned you should change the pyro connectors, I think you should have a single M80 harwin with main + drogue in the same pinouy as RA.
@BluCodeGH |
…om mosfet arming to mag switch
…t arming to mag switch arming, add text notes
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Schematic LGTM pending a few tweaks:
- Pyro connector pinout is wrong, we want main on pins 1/4 and drogue on pins 3/6
- Typically you should put the current sense shunt resistors with the main circuit rather than near the INA, makes it clearer what's going on
- Why do you have the pair of FETs that switch MAG_VOUT to +PYRO? The point of the pyro circuit is that it requires two actions to fire so there doesn't need to be any "armed" state. (Also those big FETs are really annoying to solder)
- You should set the REF of the pyro op amp to 3.3/2 volts so you can sense current flowing in the opposite direction too right? (eg PY+ shorted to GND). You might need an analog input on the REF voltage too to be able to accurately determine the zero value, I'm not sure?
- The gain of the pyro op amp might be too high? Assuming a single 1R pyro I get 6 mA through it (when we test by turning on the high side) which is 6V output at 1000V/V?
I didn't go through the full failure mode state analysis, do make sure it's up-to-date given the pyro current sensing you added and whatever opamp changes you make.
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Currently a schematic review only.