Voltage range for Trinket M0

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NChronister
 
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Voltage range for Trinket M0

Post by NChronister »

Hello. I am thinking about using the Trinket M0 for a project, and I have a few questions about voltage requirements.

First, I know the specs on the Trinket M0 specify a max battery input voltage of 6v. But it has a regulator that regulates that down to 3.3 volts. Would I be able to get away with using a 7.4 volt Li-poly battery instead of 4 AA alkaline cells?

My other question is, I want to use a radio control receiver as an input. I understand the receiver PWM signals might be either 3v or 5v depending on the receiver. Do I need to measure the pulse voltage to make sure it's only 3v, or will it work either way?

Thanks for your help!

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dastels
 
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Re: Voltage range for Trinket M0

Post by dastels »

The tutorial at https://learn.adafruit.com/adafruit-tri ... on-arduino states repeatedly that Vbat can be up to 6v.
BAT - This is a voltage INPUT pin, you can use it to connect a battery or other external power to the Trinket. It has a Schottkey protection diode so it is completely separate from the USB power input/output. You can put 3V-6V into this pin and it will be regulated down by the 3V regulator
So, no, you should not use a 7.4v battery.

The inputs are are 3.3v, not 5v.
On a Trinket M0, the GPIO are 3.3V output level, and should not be used with 5V inputs.
So, no, it will not work with 5v input levels.

Exceed either of these stated limits are your peril, or rather than of your Trinket M0.

Dave

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Re: Voltage range for Trinket M0

Post by adafruit_support_carter »

Would I be able to get away with using a 7.4 volt Li-poly battery
No. The Absolute Max input voltage for the voltage regulator is 6.5V. You should not get to that value. That's why 6 is stated as the max input range.
Do I need to measure the pulse voltage to make sure it's only 3v,
Yes. You can use a simple voltage divider to bring it down to 3.3V if needed.

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NChronister
 
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Re: Voltage range for Trinket M0

Post by NChronister »

Thanks for the voltage divider suggestion. Now I have to decide whether to add a BEC (and splitter cable since I need 7.4 volts for one of the servos) or I might use the old version Trinket instead of the M0 since it allows a higher battery voltage. (Darn I was looking forward to trying circuit python.)

In case anyone else needs to do this, here is a BEC device that should work:
https://www.amazon.com/ShareGoo-Convert ... 7656&psc=1

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dastels
 
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Re: Voltage range for Trinket M0

Post by dastels »

NChronister wrote: Tue Aug 30, 2022 2:56 pm I might use the old version Trinket instead of the M0
You will probably have problems with that. Note the warning at the top of the product description at https://www.adafruit.com/product/1501:
Deprecation Warning: The Trinket bit-bang USB technique it uses doesn't work as well as it did in 2014, many modern computers won't work well. So while we still carry the Trinket so that people can maintain some older projects, we no longer recommend it. Please check out the Trinket M0.
Dave

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NChronister
 
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Re: Voltage range for Trinket M0

Post by NChronister »

Yeah I might have to try it though. hahaha

Trinket "classic":
+ will accept 3v or 5v pwm signal
+ will accept 7.4 volt battery input
- might not work with my computer
- doesn't offer circuit python

Trinket M0:
+ works with circuit python or arduino
+ should work with my computer
- needs a 5v external regulator (BEC) & some extra wiring
- i need to find out whether my receiver pwm signal is 3v or 5v
and add a voltage divider if it's 5v

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dastels
 
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Re: Voltage range for Trinket M0

Post by dastels »

Trinket M0 *will* work with your computer. It has a modern MCU with native USB. Very different that the original Trinket. The SAMD21 MCU on the Trinker M0 is rather limited in terms of how much CircuitPython code/libraries will fit.

You might add a (non SAMD21) QtPy to your list of options. It's sort of the spiritual successor to the Trinket. The RP2040 is probably the best one for you, as you don't need WiFi or BLE capabilities.

Dave

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Re: Voltage range for Trinket M0

Post by NChronister »

Thanks. I hadn't looked into the QtPy before. The QtPy and the Trinket M0 both seem equally suitable for my application.

I measured the receiver PWM pulse voltage by taking an analog read right after the pin goes high. The result is 2.98 volts.

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dastels
 
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Re: Voltage range for Trinket M0

Post by dastels »

The QtPy with a SAMD21 is essentially the same as a Trinket M0 (but with more pins brought out, a bit smaller, USB-C, STEMMA-QT, and space on the bottom for an external flash chip). The other QtPy models have more processing power and memory. As I said, the RP2040 model is a good choice if you don't want WiFi/BLE.

Dave

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