DNA Development Blog

[BTAutoMag]

You're awesome just for #1

[new ion?]

I'm interested in this circuit.

[Curt]

Here it is, it works like this:
There are two separate current paths for Batt+, through both sides of one of THESE suckers: http://www.irf.com/product-info/data...irf9358pbf.pdf which can handle 9.2amps continuous at 20volts, and handle that much voltage at the gate. the top one is controlled by the MCU itselft by driving a teeny little N-MOSFET (can't drive direct because 3.6v << the 20v required to turn it off ) normally the MCU sits with that pin at high impedance when off, so the 180k pullup will hold that PFET off.

the bottom one is hooked up to the momentary, when depressed it connects the 10k to the 180k and forms a voltage-divider circuit which is sampled at the 'sense' pin, which needs to be an A2D, but *pff* who cares the AVR has those to burn, when off, sense will read ground, when on, it will read some positive value between .2 and 1.1v, way easy to read.

It also pulls the gate on the top PFET down to keep the power on. So when the MCU decides to cut its own power, it just de-asserts the pwr pin and viola, the PFET stops conducting and there are no paths from power to ground, not even through some 1M resistor, so zero power consumption



Also here is a video of me demonstrating it http://northarc.com/dna/power_circuit.mp4

[new ion?]

I love this forum. Learning how some things work before my classes describe them to me.

Thanks for the lesson Curt!

[BTAutoMag]

Wow I need you next time I'm wiring up the crazy stuff my customers come up with

[Lurker27]

Curt that is fantastic, thank you so much for sharing with this forum. That circuit is badly needed in paintball

[Curt]

WHOO Boy what a day. been trying to knock this out for awhile now, finally have the working circuit so I can finalize the layout, here is the button board, the OLED board (expanded to add a lip on the left and right side) and a Telemetry board.

Telemetry? yeah that is so the DNA can be used to teach a class in robotics. Those 12 channels can all drive servos, digitize input, temperature, light, A2D you name it. Also broke out the I2C bus.

Went out for quote this evening, I'll have them in process very soon.

[skibbo]

Guess I'll be busy for a night or two drawing these guys up!

Do you have a BOM for them? I think you posted a BOM for one of them already but can't remember if it was the OLED or button board.

[PBSteve]

I just came a little. What do you use to layout your boards? I monkey around in Eagle from time to time (and that looks very doable in Eagle) but I don't often do anything complex.

[evil_racecocker]

Awesome work so far, looking forward to being able to purchase several of theese to replace all my Tadao boards that the OLED screens have all fadded on.