Guys I’ve run into an issue where I can’t power the minim from the apm port. If I spike the throttle I get a slight voltage sag and the osd stops displaying info. I tried running off the same bec I use to power the apm output rail, while only leaving the RX line connected to the minim from the port. Unfortunately this is not working and the screen just glitches. If I unplug the bec from the amp, and only connect it to the minim, everything works perfectly. I real don’t want to put another bec in the plane. Any ideas?
Try disconnecting your FPV cam (I’m assuming you have one) from the Minim and see if your problem is still there. You should have a black screen from lack of video but the OSD data should still be displayed. If that is the case you have an issue with the power and ground to your camera that affecting your Minim.
I had a similar issue where whenever I pushed the throttle up beyond half on a fixed wing the image and data would start cutting out. I assumed it was vibration effecting a bad connection. It wasn’t. My camera ground didn’t go directly back to the battery. When I improved the camera ground my Minim worked fine. Minims are very picky about video signal voltage levels and if you have even a little floating ground you can lose it under high draw.
When I try to power the Minim with a BEC I run into this problem with and without the camera connected. The analog and digital side are not connected, and there in no ground loop between them.
Would there be a difference between these two setups? The problem is currently happening in the series setup, and if I unplug the BEC from the APM output, everything is perfect. I can try rewiring to a branched setup, if you guys think it would make a difference.
Branched:
Bec
/
APM MINIM
Series:
BEC – AMP - MINIM
I started off powering my Minims separately, easily blew one up, and now always power them direct from the APM/Pixhawk. I’m not sure why people still insist on powering Minims separately.
It occurs to me you say you are powering your Minim with a BEC. Typically BECs are only 5 or 6 volts. The Minim voltage for the analog (?) side is supposed to be 9 to 12 volts. It then passes through a regulator that drops it to around 5 volts or so, same as the digital side. So if you’re running this lower input voltage, any large current draw will cause a sag and hit the cutoff voltage. You would be operating the Minim at just barely enough voltage to keep it going.
Unless you have a real need for separate power, I’d suggest just bridging the two solder bridges and power it off the APM. Your problems should go away.
[quote=“OtherHand”]I started off powering my Minims separately, easily blew one up, and now always power them direct from the APM/Pixhawk. I’m not sure why people still insist on powering Minims separately.
It occurs to me you say you are powering your Minim with a BEC. Typically BECs are only 5 or 6 volts. The Minim voltage for the analog (?) side is supposed to be 9 to 12 volts. It then passes through a regulator that drops it to around 5 volts or so, same as the digital side. So if you’re running this lower input voltage, any large current draw will cause a sag and hit the cutoff voltage. You would be operating the Minim at just barely enough voltage to keep it going.
Unless you have a real need for separate power, I’d suggest just bridging the two solder bridges and power it off the APM. Your problems should go away.[/quote]
I can’t power the digital side using the APM port, that’s why I’m trying to use a bec. My APM is receiving 5.3v from from the current sensor on the input rail. By the time that voltage gets to the telemetry port, it is only at 4.75v. If I raise the throttle too fast, the voltage at the telemetry port sags to 4.6 and the minim stops displaying information. My analog side is not sagging. I’m trying to understand why the bec option works great, but only if it is not also powering the APM. My analog side is not powered by the bec.
On a side note, I have run a minim on a different plane, powering the analog side with 5v and have not run into any issues. If you solder the bridges, the analog side would be running off of 5v anyway.
Yeah, I’m pretty sure now this is your problem. You are correct that when the bridges soldered the analog gets fed directly the 5 volts from the digital side. It’s a hard connection. However if you don’t do the bridging the analog side derives its voltage from whatever you are feeding it from the analog voltage input. But before your input voltage gets to the analog side “guts” it passes through a diode (dropping the voltage 0.7 volts) and also an LM2842Y stepdown regulator. The LM2842 is set by its R1/R2 ratio to output 4.98 volts, whicgh is what the analog side really wants. Per the spec sheet this regulator takes inputs from 4.5 to 42 volts.
If you feed the analog side 5.0 volts from a BEC, you are in fact providing only 4.3 volts to the LM2842. Now it can’t step it up to 5 volts, at best it will only pass it through, but likely will drop it just a bit. It has an internal low voltage shutdown and you are just about there with this setup. It probably shouldn’t work at all, so in this case you are lucky. It may work for you powering via other BECs mostly likely due to small variations in each BEC’s output, but you are right on the ragged edge. Any voltage sag and it’s good night.
It’s not clear to me if you are using the Power Module to power the APM. That’s the best way to do it. For a fixed wing you power the APM and Minim via the Power Module, remove JP1 and power the output rail for the servos via a separate BEC or your ESC’s BEC. This should work fine.
If for some reason you feel you absolutely must power your Minim’s analog side separately, you could use a Castle Creations 10 Amp BEC which has an adjustable output up to somewhere around 9 volts. Or you could use whatever BEC you have on hand and use a small IRC or Pololu 12 volt step up converter (very small) to kick the voltage you are feeding the analog side up to 12 volts. Either of these two methods should also make your problem go away.
I used to power my MinimOSD from the APM but had a problem with it freezing and/or shutting off all the osd and just leaving the video feed. After trying every configuration I could I soldered the digital and analog sides together and replaced the 5v supplied by the apm with a dedicated ubec (no power connected to the other side at all, just signal and ground) and have never had a problem since.
I have since used the same setup on my APM plane (originally using the motor esc’s bec for the APM now using a PM) and my rebuilt Pixhawk (with PM) quad with 0 problems.
[quote=“OtherHand”][quote=“ZephyrChris”]
On a side note, I have run a minim on a different plane, powering the analog side with 5v and have not run into any issues. If you solder the bridges, the analog side would be running off of 5v anyway.
[/quote]
Yeah, I’m pretty sure now this is your problem. You are correct that when the bridges soldered the analog gets fed directly the 5 volts from the digital side. It’s a hard connection. However if you don’t do the bridging the analog side derives its voltage from whatever you are feeding it from the analog voltage input. But before your input voltage gets to the analog side “guts” it passes through a diode (dropping the voltage 0.7 volts) and also an LM2842Y stepdown regulator. The LM2842 is set by its R1/R2 ratio to output 4.98 volts, whicgh is what the analog side really wants. Per the spec sheet this regulator takes inputs from 4.5 to 42 volts.
If you feed the analog side 5.0 volts from a BEC, you are in fact providing only 4.3 volts to the LM2842. Now it can’t step it up to 5 volts, at best it will only pass it through, but likely will drop it just a bit. It has an internal low voltage shutdown and you are just about there with this setup. It probably shouldn’t work at all, so in this case you are lucky. It may work for you powering via other BECs mostly likely due to small variations in each BEC’s output, but you are right on the ragged edge. Any voltage sag and it’s good night.
It’s not clear to me if you are using the Power Module to power the APM. That’s the best way to do it. For a fixed wing you power the APM and Minim via the Power Module, remove JP1 and power the output rail for the servos via a separate BEC or your ESC’s BEC. This should work fine.
If for some reason you feel you absolutely must power your Minim’s analog side separately, you could use a Castle Creations 10 Amp BEC which has an adjustable output up to somewhere around 9 volts. Or you could use whatever BEC you have on hand and use a small IRC or Pololu 12 volt step up converter (very small) to kick the voltage you are feeding the analog side up to 12 volts. Either of these two methods should also make your problem go away.[/quote]
The analog side on this plane is powered by 12v, I’m 99% sure that the issue is on the digital side. I have tried bridging both sides and running off the telemetry port, and got the same results. The only setup that fixed it was to provide the digital side with 5v from my bec. But I still have the same question: Why is the bec solution only working if I don’t have it also powering the APM? Is the RX line from the minim to the telemetry port creating a loop through the power modlel and back to the battery? I could solve my problem by installing another bec, and using it only for the minim. I set up a temporary test like this and it worked nicely. But I do not want to use another bec, I want to power the output side of the APM and the digital side of the minim with the same bec.
Setup:
APM, Jp1 removed and power module supplying the input side.
7 amp BEC powering the output rail, for the servos (and hopefully the minim.)
The analog side of the minim is receiving power from and Immersion 2.4vtx that is receiving power directly from the 4s pack. The vtx outputs 5v, and I run a Pololu 12v stepup converter to power the minim and cam.