Raven and Eggfinder: Can the eggfinder output drive a Raven?

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wfcook

Mayhem Rocketry, LLC
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I notice that the eggfinder has a 3.3V output, which in theory would allow me to run both off of a single 2S 7.4V LiPo, but I know that the Raven has some limits on the amount of current it can handle and Adrian discourages the use of large LIPOs when used directly. Is it possible to drive the system this way and handle the ejection charges without burning out the Raven?
 
The eggfinders 3.3v isn't designed to handle the current of an ematch you will likely damage it
 
Gotcha. Isn't it supposed to drive the eggtimer though? How does the eggtimer Fire charges without destroying the Tx unit in the process?
 
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It operates the logic, the full battery voltage still fits the charge
 
Ahhhhh. That 'splains it thanks very much.

I need an eggtimer TRS with accelerometers for velocity measurement and which is rated for high G loads. Dang it.

Or a raven with a GPS.
 
The regulator in the Eggfinder is good for 800 mA, which is quite a lot, but not enough for an ematch unless you're using a Q2G2. If you use Q2G2's anyway you might want to ground test it to see if it's going to work. The Raven almost certainly has its own voltage regulator, and that may or may not present a problem depending on the voltage that the Raven's logic operates at. If it's at 2.8V (a common voltage that works well from a 1S LiPo), it might work; if it's at 3.3V, the voltage drop through its regulator might not provide enough voltage to reliably power its logic.
 
Gotcha. Isn't it supposed to drive the eggtimer though? How does the eggtimer Fire charges without destroying the Tx unit in the process?

The Eggtimer (and the TRS) are designed to be used with a separate battery for the deployment channels, they are completely isolated from the logic by optoisolators. They don't even share a common ground. Having separate logic and deployment power completely eliminates brownouts caused by deployment igniter shorts. You can connect the LOGIC of the Eggtimer to an Eggfinder's 3.3V output and it will be just fine, but I wouldn't run the deployment side from it too.

You COULD run the deployment power from the 2S LiPo that you power the Eggfinder from, just make sure it's big enough. I recommend that the current rating x the "C" rating is at least 10x the all-fire current of your igniter. For example, a 400 mAH 2S LiPo rated at 25C can put out 10A, so if your ematch's all-fire current is 1A you're gonna be fine.
 
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