Faulty EasyMini?

[TXJeff]

My brand new EasyMini: I watched the Apogee videos, connected everything and a test igniter. As soon as power is switched on it fired the igniter!
So I bench checked it with my meter to confirm that both sides (main and apogee) are hot as soon as power is switched on. It connects to my laptop fine, everything looks good otherwise. Checked it all again in disbelief.
Any ideas? Was there a faulty batch of these or something?

 

[Banzai88]

I have a metric butt ton of these things, V1, 2, and 3s.....never seen one do that, that's for sure!

After double checking the wiring, I would be contacting Altus through their web page/store contacts and/or the Altus mailing list.

From what I've seen of other folks' issues, they'll get you sorted out quickly and to your satisfaction.

 

[Voyager1]

Similar issues have been experienced by others. Check out the previous thread on this subject.

https://www.rocketryforum.com/threads/easy-mini-problem.172373/

 

[thehemi]

Jeff,

Did you contact Altus about this? What was the resolution?

I just built my first setup using an EasyMini and I'm experiencing the same thing. The moment I turn on the unit, I'm getting 9 volts to both of the terminals.

Thanks,
Scott

 

[Voyager1]

Jeff,

Did you contact Altus about this? What was the resolution?

I just built my first setup using an EasyMini and I'm experiencing the same thing. The moment I turn on the unit, I'm getting 9 volts to both of the terminals.

Thanks,
Scott

Be careful where you measure the output voltage on the EasyMini output terminals. The + terminals are actually connected to the battery. The - terminals are switched by the output MOSFETs.

If you’re measuring between the + output terminals and ground, then you will see 9V there when it’s switched on. To confirm whether there is a problem, with the altimeter off, connect some ematches to the main and drogue outputs, then switch on. If all is ok, then nothing will happen; if not ok, then they will fire.

 

[thehemi]

I'm attaching a photo of where I'm reading the 9V. To clarify, I'm not talking about the terminals on the EasyMini itself, but the terminals on the junction block for the igniters. I'm getting 9V all the time on these. Maybe I don't understand, but this doesn't seem right.

Thanks,
Scott

 

[Voyager1]

I'm attaching a photo of where I'm reading the 9V. To clarify, I'm not talking about the terminals on the EasyMini itself, but the terminals on the junction block for the igniters. I'm getting 9V all the time on these. Maybe I don't understand, but this doesn't seem right.

Thanks,
Scott

Ok. The main and drogue output terminal don’t have +/- markings as I suggester above. My mistake there. However, what I said about the outputs still stands. One side of each output is connected to the battery voltage; the other side to the MOSFET switch. However, there is additional circuitry on the MOSFET side connection that references that terminal point to ground. These are the continuity sense circuits for the main and drogue outputs.

So, with one side of the main or drogue terminal pair connected to the battery voltage, and the other side of each pair connected to ground via the continuity sense circuits, you will measure a voltage across each output terminal pair. That’s the continuity sense voltage. If it’s working correctly it won’t ignite anything.

As I mentioned earlier, if you’re concerned about it, do the test I suggested above to confirm whether the outputs are good, or faulty.

You should seek advice from Altus Metrum, in any case.

 

[thehemi]

OK, I think it could have been explained even easier for a simpleton like myself.

It's not the volts but the amps which fire the igniters. There's 9V in the circuit, but almost zero amps. When I trigger them to fire through the software, the amps momentarily spike.

I still need to bench test with some ematches, but it looks like I should be OK. It was definitely my lack of understanding of how these work. I appreciate the feedback!

Thanks,
Scott

 

[Voyager1]

OK, I think it could have been explained even easier for a simpleton like myself.

It's not the volts but the amps which fire the igniters. There's 9V in the circuit, but almost zero amps. When I trigger them to fire through the software, the amps momentarily spike.

I still need to bench test with some ematches, but it looks like I should be OK. It was definitely my lack of understanding of how these work. I appreciate the feedback!

Thanks,
Scott

Yes, in this case it's the current that does the work.

When you have an igniter or ematch connected to the main or drogue terminals, that completes a high resistance series circuit between the battery and ground, via a couple of continuity sense resistors. The current through the sense circuit (and the igniter) is very low, perhaps up to a few mA, or less. The processor reads the voltage from this resistive divider and determines whether there is continuity.

If all is good, when the altimeter activates the output MOSFET switch, it connects the lower side of the igniter to ground, effectively bypassing the continuity sense resistors. You now have the (nearly) full battery voltage across the low resistance of the igniter. The high current (a few Amps) through the igniter then does its job!