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Question about M4 Express and power delay.
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Question about M4 Express and power delay.

by ppespepe on Sat Apr 03, 2021 3:53 pm

Hello everyone,

This is my first post, hope I'm pointing to the right place. :D

I learning to use CIrcuitPython using some Metro M0 and M4 Airlift Lite so expect a basic if not silly question ;-) . I'm trying to use some multi-sensor called Ambimate MS4. The thing is, I think the device is poorly designed and needs a delay in the 3.3 volts in for it to be able to recognize all its internal sensors. Since it is a 3.3v sensor I thought I could use a digital port to turn it on but it won't work. Is there a way to interrupt the 3.3v output for a second or two after the Metro is turned on? A realy might work but relays I know are huge and circuit space is a concern since I want to mount everything on a hat. Right now I'm using regular solder-less breadboard.

I'm have put the following code at the beginning for me to disconnect the Ambi, then connect while it is still blinking. If I leave it on the 3.3v line, it will forget some of its internal sensors... and sometimes it may believe its a celery... other than that it kinda works :D

led = digitalio.DigitalInOut(board.D13)
led.direction = digitalio.Direction.OUTPUT
for delay in range(0, 15):
led.value = True
time.sleep(0.5)
led.value = False
time.sleep(0.5)

3c215b8a-df93-4a78-a2a2-ae5ed0e83d02.JPG
3c215b8a-df93-4a78-a2a2-ae5ed0e83d02.JPG (182.76 KiB) Viewed 262 times


Thanks in advance!

PP

ppespepe
 
Posts: 4
Joined: Sat Mar 20, 2021 3:13 pm

Re: Question about M4 Express and power delay.

by dastels on Sat Apr 03, 2021 5:21 pm

You could use a FET. Have a look at the POWER/D10 circuitry on the PropMaker wing: https://learn.adafruit.com/assets/69243.

What makes you think delaying 3.3v would help?

Dave

dastels
 
Posts: 6786
Joined: Tue Oct 20, 2015 3:22 pm

Re: Question about M4 Express and power delay.

by ppespepe on Sat Apr 03, 2021 6:26 pm

Thanks Dave,

I'm not sure I understand your answer but I'm definitely not an electronic connoisseur. I mean, apparently that board has the required circuitry on the GP10 pin but I'm using a Metro M0 and or M4 so I don't think I'll able to figure out how to use a mosfet to replicate that port behavior. :-(

What makes me think delaying 3.3v DC will help? two things:

- I opened a case with the sensor vendor some time ago and the told me that.
- Even though I could not believe that was true, I tried and is true...if ground and power are connected at the very same time, it fails to recognize the sound sensor and sometimes even the gas sensors. This is not a problem with the cheaper 4 sensors only version but it does happens with the more expensive all-in versions.

Look:

2021-04-03_15-34-26 1.jpg
with GND and 3.3 applied at the same time.
2021-04-03_15-34-26 1.jpg (26.2 KiB) Viewed 259 times


2021-04-03_15-40-54 2.jpg
when I disconnect the 3.3v cable and connect it again a couple of seconds after Metro is turned on.
2021-04-03_15-40-54 2.jpg (25.78 KiB) Viewed 259 times


Perhaps I'm just trying to bite more than I can chew and I'll just need either put a small sliding switch or just throw those expensive sensors because this is a design failure in my humble opinion... this is by no means my Metro's fault... its just the multi-sensor... :-)

Thanks!

PP

ppespepe
 
Posts: 4
Joined: Sat Mar 20, 2021 3:13 pm

Re: Question about M4 Express and power delay.

by dastels on Sat Apr 03, 2021 8:43 pm

I agree that that is very odd behavior.

It sounds like it's more trouble than it's worth.

Dave

dastels
 
Posts: 6786
Joined: Tue Oct 20, 2015 3:22 pm

Re: Question about M4 Express and power delay.

by ppespepe on Sat Apr 10, 2021 8:54 pm

Well, I didn't know about Mosfet and it is not like i know a lot now but learning is what I'm after and now it works! :D

It was hard but the SMD adapter made it less hard to make the connections:
f160d653-59cb-4b64-8aba-51279080a537.JPG
f160d653-59cb-4b64-8aba-51279080a537.JPG (107.39 KiB) Viewed 239 times

959273e3-7d3b-4bd7-81a0-a434c3226bd6.JPG
959273e3-7d3b-4bd7-81a0-a434c3226bd6.JPG (233.65 KiB) Viewed 239 times


And the result:
2021-04-10_19-40-56.PNG
2021-04-10_19-40-56.PNG (549.53 KiB) Viewed 239 times


Now I only need to make MQTT work!

Thanks for the guidance!

ppespepe
 
Posts: 4
Joined: Sat Mar 20, 2021 3:13 pm

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