Making a Portable power supply

Thread Starter

Lorvuk

Joined Jan 21, 2021
5
Hi I'm working on a project where I want to be able to control 6, 5V rated push/pull solenoids with a raspberry pi 3 model B. I used circuit IO to layout the circuit diagram needed but I want to make the project portable. And since the current draw from one solenoid is 1.1A, total current draw from 6 of them is 6.6A that means I would need a (6.6A*5V=33W) 33W source to power all of the solenoids and a separate source for the raspberry pi 3 which draws 3.4W. My question is how would I power them in order to make the project portable ?


Circuit IO diagram --> https://www.circuito.io/app?components=9443,11015,11015,11015,11015,11015,11015,200000
5v Solenoid --> https://www.adafruit.com/product/2776
 

dl324

Joined Mar 30, 2015
12,871
Welcome to AAC!

  1. What is your definition of portable?
  2. How long to you want the solenoids to be energized and what is the duty cycle?
  3. Do you plan to charge the batteries at the work site?
 

AnalogKid

Joined Aug 1, 2013
9,254
My question is how would I power them in order to make the project portable ?
With batteries. Not trying to be snarky - that is the answer. If you are asking about the tradeoffs of various battery chemistries, and the complexities of chargers for those chemistries, then tell us what you know and what you need to know.

ak
 

Thread Starter

Lorvuk

Joined Jan 21, 2021
5
Welcome to AAC!

  1. What is your definition of portable?
  2. How long to you want the solenoids to be energized and what is the duty cycle?
  3. Do you plan to charge the batteries at the work site?
Portable meaning i want to be able to fit eveything into a hanfheld box( any size will do as long as its handheld). I want the solenoids to be able to operate as long as possible given the spacing of what i have in mind so whatever battery that is small enough so eveything can fit in a hand held box. Charging the batteries would be the most economical choice so yes i would like to do that.
 

Thread Starter

Lorvuk

Joined Jan 21, 2021
5
With batteries. Not trying to be snarky - that is the answer. If you are asking about the tradeoffs of various battery chemistries, and the complexities of chargers for those chemistries, then tell us what you know and what you need to know.

ak
Are my calculations for my power needs correct? and how would i hook up a battery to the circuit i have above? i dont know if for example hooking up a 34 watt battery to the circuit would cause anything to break?
 

Sensacell

Joined Jun 19, 2012
2,822
34 watts is about what my big gaming laptop draws from it's battery- and it lasts only about 2 hours when new and fresh.

You need a very efficient voltage regulator for the longest life - a DC-DC switching regulator.

Are you sure you cannot replace the solenoids with something less power-hungry?
Solenoids are just terrible at converting electrical energy into mechanical work, I mean the worst.
 

AnalogKid

Joined Aug 1, 2013
9,254
What is the minimum run time you can tolerate? Without that information, there is no starting point.

Batteries are sized in amp-hours (Ah or A-h). For any nominal output voltage you can convert this to watt hours - or work backwards. If you want to power 34 watts of stuff from a 14 V source (four LiPo cells in series), 34 W means 2.4 A If the switching 12 V to 5 V buck regulator is 81% efficient, that raises the 2.4 A to 3.0 A. That's 3.0 A-h (3000 mA-h) of energy for each operational hour, about the limit for a bank of four, high-end 18650 lithium batteries.

ak
 

Dodgydave

Joined Jun 22, 2012
9,951
Work out your current draw for say an hour, then you can start to select a battery to give over that capacity, example if you need 2A in an hour, then you're going to need 2Ah battery capacity at least.

Then you can look at types such as Lithium, Lifepo, SLA..
 

AlbertHall

Joined Jun 4, 2014
11,309
To minimise total power consumption you could apply full voltage briefly toa solenoid and then reduce the voltage to just hold in the solenoid. Solenoids get more powerful as they pull in. It would make the circuitry more complicated though.
 
Top