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Topic: How to power a 5v trinket? (Read 615 times) previous topic - next topic

kandjar

I very recently got into electronics, and I found a lot of "beginner"'s tutorials which were fantastic.
And a lot of "very advance ones", sadly I'm king of missing the middle part :-)
Especially when it comes down to powering up an Arduino with a rechargeable battery or using AAs.

The most scary aspect is when you ready: "Oh and be careful, if you're doing it wrong, it's gonna blow up".  This type of sentence doesn't make me want to do a bunch of "try and error" tests :D

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In other words, if anyone can redirect me to some beginner like tutorials regarding powering up a system, that'd be great.
And/Or if you could help me finding what I need to do to power my own project, that'd be even more awesome!!!

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My first project is basically a small LCD game system for my daughter (hence the importance of the safety here)

I'm using:
- an trinket pro 5v.
- a 0.97'' LCD screen powered up by the trinket 5v output.
- and a bunch of buttons/resistors...

Nothing crazy.

I'm not sure whats the best way to power this up, in "efficient manners"; should I go for a rechargeable battery? Some button batteries? AAA ones???
Ideally something small is better, I want to fit the whole thing in a Altoids box.

ChrisTenone

The safest and possibly easiest way to power your Pro Trinket is with 3 AAA cells, fed directly into the 5 volt pin on the board. True, it's only 4.5 volts, but that will be sufficient to power it up, and even run a few LEDs.
Atmosphere carries combustion vapors to places where they will do good instead of harm - Mike Faraday's 'History of a Candle': https://www.youtube.com/watch?v=6W0MHZ4jb4A

Whoops ::)

kandjar

The safest and possibly easiest way to power your Pro Trinket is with 3 AAA cells, fed directly into the 5 volt pin on the board. True, it's only 4.5 volts, but that will be sufficient to power it up, and even run a few LEDs.
You don't need power regulator for it?


ChrisTenone

You don't need power regulator for it?


Nope. Just give it 4.5 volts, and it will run just like it's got 5 volts. Take a look at the graph in this post. The 328 (the chip in the protrinket) will run at 16MHz down to about 4 volts.

If you do want to go through the Vin pin, then give it a minimum of 6 volts (4 aaa cells). But now you are nearly filling the Altoids can with batteries. Again, if you use a 3V protrinket, you can get away with 2 batteries.

An alternative way of powering it if you want to use a rechargable LiPo battery is to get Adafruit's LiPo backpack, but it is operating a bit below optimal. The backpack is designed for a 3V protrinket, but does work. It's perfectly safe when hooked up correctly.
Atmosphere carries combustion vapors to places where they will do good instead of harm - Mike Faraday's 'History of a Candle': https://www.youtube.com/watch?v=6W0MHZ4jb4A

Whoops ::)

ChrisTenone

By the way, here are a few of the Altoids toys I've made:



My friends and relatives get them as Christmas/birthday presents.
Atmosphere carries combustion vapors to places where they will do good instead of harm - Mike Faraday's 'History of a Candle': https://www.youtube.com/watch?v=6W0MHZ4jb4A

Whoops ::)

LandonW


ChrisTenone

What do these toys do?
Clockwise from the top left, a device to throw - and interpret - the IChing, a scrolling clock/calendar that recharges from the solar cells in my office window, an hourglass that utilizes a TXO made by epoxying a thermistor to an 8 MHz crystal on a tiny 85 (it's accurate to 100th of a second), a 4 band spectrophotometer (UVa, UVb, visible and IR) and a photographic exposure meter with aperture, shutter speed and iso control. I've got some more (about 18 in all) but haven't photographed them yet.

I'm working on a dice roller now, that uses a 'true random number' generator.
Atmosphere carries combustion vapors to places where they will do good instead of harm - Mike Faraday's 'History of a Candle': https://www.youtube.com/watch?v=6W0MHZ4jb4A

Whoops ::)

kandjar

The little projects are awesome :D

It's interesting to see that you've been using some sort of breadboard for the circuit.


I'm currently playing with protoboards, I'm designing the buttons layout on it.


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And now I wonder if I shouldn't buy a 3v trinket for power simplification and space efficiency.


FYI:
I'm working on a lilttle Yahtzee games, using SSD1306 bi-color screen :)
The screen support 3v or 5v as power source.


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Also, would it work with button batteries? like LR44?

avr_fred

#8
Jan 18, 2018, 04:38 am Last Edit: Jan 18, 2018, 04:41 am by avr_fred
While I cannot point you to a specific tutorial, the most important part of wiring power is to get the polarity correct. Perhaps it is time to purchase a low cost digital multimeter. Using the multimeter, you can (safely) confirm connections and polarities before applying power to a circuit. As you grow with the hobby, a multimeter will become your most basic troubleshooting tool.

A $5 cheap-o from Harbor Frieght is perfectly fine for Arduino related work but please don't use the cheap Chinese meters on household voltage, they're not super safe, is especially the probes.

As an side note about polarity, the Trinket has a diode on the VBAT input connection. This prevents any damage to the board if it is connected to reverse polarity since current can only flow one way through a diode, the plumbing analog of a check valve. But, if you use 3 batteries for a 4.5 volt supply and connect it to the +5V connection, there is no diode. Connecting the polarity incorrectly here will usually damage the voltage regulator and or processor. There is no diode used in this second case as the diode causes a small drop in voltage, only about 0.3 volts, but that could represent hours to days of run time with a battery.

LR44: unsuitable, too low in power delivery ability. A CR2032 is about the minimum for a disposable cell.

kandjar

While I cannot point you to a specific tutorial, the most important part of wiring power is to get the polarity correct. Perhaps it is time to purchase a low cost digital multimeter. Using the multimeter, you can (safely) confirm connections and polarities before applying power to a circuit. As you grow with the hobby, a multimeter will become your most basic troubleshooting tool.

A $5 cheap-o from Harbor Frieght is perfectly fine for Arduino related work but please don't use the cheap Chinese meters on household voltage, they're not super safe, is especially the probes.
I did.
I had an old multimeter which I did not trust the reading, so last week, I bought an: AstroAI Digital Multimeter, TRMS 6000.

As an side note about polarity, the Trinket has a diode on the VBAT input connection. This prevents any damage to the board if it is connected to reverse polarity since current can only flow one way through a diode, the plumbing analog of a check valve.
Looking at this pinout diagram:
https://cdn-learn.adafruit.com/assets/assets/000/025/645/medium800/trinket5.png?1432753823
I'm guessing that the VBAT input connection is the top right one above the ground (labeled: BAT+)

But, if you use 3 batteries for a 4.5 volt supply and connect it to the +5V connection, there is no diode.
...
I'm not sure which input you're talking about here ???

...as the diode causes a small drop in voltage, only about 0.3 volts, but that could represent hours to days of run time with a battery.
Oh!! Hence why they advise 5.5V min on it. Coz of the voltage drop...

LR44: unsuitable, too low in power delivery ability. A CR2032 is about the minimum for a disposable cell.
I was thinking using multiple LR44 in serie...
But considering the CR2032 is 3V, it may be better to use 2 CR2032 in serie to get sufficent voltage to the arduino.

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