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The Dual-Battery Option
Using separate batteries for the Proton's computer and deployment side has some advantages,
and one disadvantage. The disadvantage is that it's going to take more stuff... one more battery,
one more connector, and possibly, one more switch. The advantages that: 1) You can use a
different voltage battery than the computer side, which you may want to do for servos; and (the
big one) 2) No matter what happens on the deployment side, including a complete loss of battery
power, it's not going to affect the computer side. This is the same philosophy behind the dual-
battery architecture on other Eggtimer Rocketry flight computers such as the Eggtimer Classic
and the Eggtimer TRS.
Some other flight computers use a big capacitor on the power output, with a single battery to
prevent brownouts. This protects against momentary disconnects such as a glitch due to G-
forces when your drogue deploys, but it won't protect against a longer-term brownout such as a
shorted ematch after firing. Once that capacitor drains, your altimeter is done. With the dual-
battery setup, if you have a short on the drogue it's going to cause a high current drain for a few
seconds until either the processor shuts the output transistor off, or until the transistor blows (not
likely, by the way). Either way, that high current draw is going to stop. Unless your battery gets
totally fried during these few seconds (also not very likely...), when the command is sent to the
main to fire it's going to work.
To wire up your Proton for dual-batteries, wire the +/positive side of the battery connector to the
DP+ pad (next to the BATT pads), and the -/negative side of the battery to the DP- pad (located
between the deployment output pads). Leave the B+ pad unconnected. If you are going to be
using a separate disconnect switch for the deployment battery you will generally wire it in series
with the +/positive side, so that it goes between the DP+ pad and the +/positive lead of your
battery connector.
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