PSAS/ CanNodeSectionAppPower

OLD OLD OLD Avionics Power System Page

AvionicsPowerSystemLv2 - New system page for LV2's APS... in design mode right now.

BatteryResearchLv2 - research into Li-Ion/Li-Polymer batteries for LV2
ChargerIcResearchLv2 - research into charging ICs for Li-Ion/Li-Polymer batteries
AandTBatteriesLv2 - Information (and pictures) on the A&TB Li Ion batteries from Electronic Goldmine


The APS is the power system of the LV2A's avionics. It's a pretty simple system of a prototyped power distribution board and a misc. CAN node board. It also has:

Firmware Page: CanNodeFirmwarePwr

Battery datasheets (we have a dozen of the kodak's):

APS Behaviours

Power Switch:

Umbilical Cord:

APS modes:

Since the misc CAN node is always powered on so minimize power usage, especially when on battery and avionics system is switched off. Power modes of the APS:

CAN Messages (see CanBusIDs for details):



Hardware To do:

  1. Change UMB resistor to 47K and add 100nF cap
  2. Test test test

Power consumption

What the HELL is our power consumption? See also the BatteryPack discussion.

This table is current from the *battery pack (12V? nom.), not into the device (which may use a DC-DC converter).

System Imin Iavg Imax Validity
ATV: CAN Node (idle) 0.035 Measured
ATV: Camera 0.125 Measured
ATV: Overlay board 0.053 Measured
ATV: 1.27 GHz FM TX 0.122 Measured
ATV: 1.3 GHz Power Amp 1.211 Measured
FC: PC104 Stack 0.415 Measured
FC: 802.11b PCMCIA ? -
FC: 2.4GHz Power Amp 0.629 .900 Measured, data sheet
APS: CAN Node 0.012 0.047 Measured
GPS: CAN node 0.025 Measured
GPS: GPS (low pwr mode) 0.092 Measured
GPS: 1.5 GHz preamp 0.125 Measured
IMU: CAN node 0.025 Measured
IMU: IMU 0.070 Measured
REC: CAN node ? -
REC: 2m board ? -
REC: HAP battery Chrgr ? -
TOTAL 2.85 -

Shunt resistor selection

Hnmmmm. So at - call it 4A - that means if we use a 0.050 ohm shunt that's a 0.2V drop and 0.8W of dissipated power. Eech! Sucks. So let's parallel two up and get 0.025 which gives us 0.1V of drop and 0.4W of dissipated power. Seems better, so let's stick with it.

To get 5V full scale out of the INA168 we need a gain of 5V/0.1V = 50 which also seems ok since that implies R(L) = 50*5kohm = 250kohm. But we're using LM358's which have a minimum v_out of 3.5V so we'll use something smaller - 150kohm which will give us a gain of 30, which gives us 0.75V/A. That's 3.75V @ 5A so we can go a bit over our allotted current and not hit the rail. We happen to have 100k 0.1% in an 0805 package so 2x 100k in parallel + 1x 100k to give us 150k.

Low Pass Filters

We decided to try and use real LPF's on the bus voltage and current in order to get useable values of system performance. We chose a f3db = 1KHz, 4 pole Bessel filter in a sallen-key configuration. We choose that LPF, along with a sampling rate of 15KHz, in order to get 10bit performance out of our ADC. Yeah, right we'll get 10bits with the way this thing is hacked up ;)

We used Microchip's Filter Lab to come up with RC networks around the LM356's.

SmartBatteriesLv2: Past thoughts on using smart batteries