Advice for DIY Timer

[crdimitro]

I was looking at the Art Controller Relay Board Kit or the "Three Fives" Discrete 555 Timer Kit listed on adafruit.com.
I would like to power an adafruit power boost 500 for 30 minutes every 24 hours or have the flexibility to change those variables using the same AA battery power source.
If these will not work, can you point me to a kit that I should use that will allow me to do that.
Thank you

[Lakitna]

The 555 timer kit you mentioned is a show model, far bigger than a normal NE555. Though the kit does work, it is not intended to use in projects.
Besides the kit you've listed being a show model, the 555 timer is a device that gives clock pulses. It is not a full clock. By changing the external components linked to the 555 you can change the on and off time. If you want to know more about the 555 you can check this Instructable all about it.

The Art controller relay board will work, but is not the best fit in my opinion. All you really need is some kind of microcontroller with a transistor. Especially if the time the power booster has to be on doesn't come down to minute precision. If you need it very precise you'll have to add a RTC.
Back to the microcontroller. Because you only need a single output (the transistor) you can use the smallest microcontroller available. In the Adafruit store that's the Trinket. A standard transistor should do the trick.
You can then proceed to program the Trinket to open the transistor for 30 minutes, and close it again for 23 hours and 30 minutes.

[crdimitro]

Thank you for that. In studying it there was a 3v and 5v. the PowerBoost 500 works on 1.8v + and steps up to a 5v. It is powered by 3x AA. Which trinket would I need the 3v or 5v

[Lakitna]

That can actually depend on the transistor you will be using and your power supply. A 3,3v Trinket has max 3,3v coming out of a output pin while a 5v Trinket can supply 5v over the same pin. The question is at what voltage the transistor switches. I took a look at the datasheet of the previously mentioned transistors which states a Base-Emitter Saturation Voltage (Vbe) of 0,6v - 1,2v. This is well under 3,3v as well as 5v so using both Trinket shouldn't be a problem.
The next thing is the power supply of the Trinket. You will be powering the Trinket with 3 AA batteries so 3 * 1,5v = 4,5v. Because this isn't a pure 3,3v or 5v we'll have to use a voltage regulator. Luckily this is built in to the Trinket! As you can find on this page the voltage regulator pin of the 5v Trinket can take an input of 5,5v - 16v and the 3,3v Trinket requires 4,3v - 16v. This means that the 5v Trinket can not be properly powered by 3 AA batteries, while the 3,3v can.

Bottom line: The transistors work with both Trinkets, but because of the 3 AA battery power supply the 3,3v Trinket will work better for you.

[crdimitro]

Thank you so much for all of your help, instruction and advice. Now I'm just waiting for them to arrive and can't wait to test it out.

[Lakitna]

No problem! Please show me the final result when you're done :)