Feather M0 GPIO current

Please tell us which board you are using.
For CircuitPython issues, ask in the Adafruit CircuitPython forum.

Moderators: adafruit_support_bill, adafruit

Please be positive and constructive with your questions and comments.
Locked
User avatar
mwpmorris
 
Posts: 6
Joined: Mon Dec 10, 2018 9:39 am

Feather M0 GPIO current

Post by mwpmorris »

Hi,

I'm considering a Feather M0 (with WiFi) for a small footprint project that I have in mind. The feather will need to individually open/close the contacts of a bank of latching relays, so by pulse rather than a constant HIGH feed. I'm not sure if the feather would be able to energise the coil however as I can't find the current output specs for its microcontroller. Does anyone know this? Is it limited by the capabilities of the Feather's regulator? I'll be needing to bypass this and feed from an external regulator anyway as my supply is 16-17v.

These are the relays that I'm considering, looks like they need 33mA to energise the coil:
https://www.mouser.co.uk/datasheet/2/30 ... 128313.pdf

Many thanks!

User avatar
oesterle
 
Posts: 806
Joined: Tue Sep 17, 2013 11:32 pm

Re: Feather M0 GPIO current

Post by oesterle »

Hi, mwpmorris!

I'd avoid connecting any relay directly to a GPIO on any microcontroller. A problem with relays is flyback, which can permanently damage your microcontroller. Instead, I'd consider using a Adafruit Non-Latching Mini Relay FeatherWing or latching version instead, both of which have built-in power and flyback circuitry.

Alternatively, you could build your own relay circuit; Brent Rubell shows how in the Experimenter's Guide for Metro: CIRC11: Larger Loads with Relays, in the Adafruit Learning System.

Cheers,

Eric

User avatar
XRAD
 
Posts: 754
Joined: Sat Nov 19, 2016 3:28 pm

Re: Feather M0 GPIO current

Post by XRAD »

I have used these in prior projects without issue:
http://wiki.sunfounder.cc/index.php?tit ... lay_Module

there are 2, 4, and more relay banks available. They get their own 5v supply, you just have to send a HIGH or LOW signal via a GPIO pin to make them close or open (one pin -one signal-one relay) , can't remember if they worked on 3.3v signal....

or you could use I2C 8 channel analogue multiplexer to drive 8 relays off one GPIO pin ......

or eight channel I2C digital multiplexer to trigger another I2C processor to hold relay 'closed' / 'open' for whatever length of time
Last edited by XRAD on Tue Dec 11, 2018 10:29 am, edited 1 time in total.

User avatar
mwpmorris
 
Posts: 6
Joined: Mon Dec 10, 2018 9:39 am

Re: Feather M0 GPIO current

Post by mwpmorris »

Thanks very much for the replies, I should probably done a bit more reading before posting.... I think I’ll end up using a driver IC as the final project needs to be very small.

User avatar
XRAD
 
Posts: 754
Joined: Sat Nov 19, 2016 3:28 pm

Re: Feather M0 GPIO current

Post by XRAD »

depending on V and amps, you could just use NPN's or PNP's......or NPN array chip for multi-channel

User avatar
mwpmorris
 
Posts: 6
Joined: Mon Dec 10, 2018 9:39 am

Re: Feather M0 GPIO current

Post by mwpmorris »

Thanks for the replies everyone. You can probably guess that I'm a relative beginner at the electronics side of the Arduino world.

My project is a very small switching box that can switch a >16v battery supply to 6 separate outputs. I'm hoping to use an ESP8266 or similar so that the switching can be done on a smartphone.

Originally I had earmarked some MOSFETs for the switching, but came to the conclusion that I didn't want to rely on a microcontroller to keep the MOSFETs open. The switching is critical and I would need the switching to survive any crashes / failures, hence the "physical" switches - latching relays.

Couple of questions...... I have some very small relays earmarked, would I simply be able to solder some flyback diodes across each coil?

Alternatively, my interest in a relay driver IC was piqued by XRAD's post above. Something that will deal with driving a bank of relays "all in one" over I2C from the Arduino would be ideal. A DIP package even better (so that I can breadboard it) - any suggestions?

Thanks again!

Locked
Please be positive and constructive with your questions and comments.

Return to “Feather - Adafruit's lightweight platform”