I am currently working on a project involving the use of several linear actuators which I hope to control using the Arduino. I am also using relays to control the actuators. What I am concerned about is the power supply that I should be using to power all the actuators, relay coils and the arduino (along with some other electrical components connected to the arduino such as the ultrasonic sensors and LCD display). Preferably, I would like to use a single power source to power all the components.
The actuators that I am using are the L16-P linear actuators by Actuonix rated at 12V and a current draw of <100mA (based on the amount of load it is lifting). The power is cut when the desired position is reached after extending or retracting. 3 of such actuators are used. The 4th actuator is a heavy duty actuator rated at 12V/24V (I am still researching on an exact one to use) but requires a high full load current draw of 20A. I am using the PA-17 Heavy Duty Actuator by Progressive Automations as an example. These 4 actuators are controlled by a 12V 8 channel relay module with 2 relays for each actuator to allow control for moving in both directions. I am using a Arduino MEGA 2560 in this set up, along with some other components such as a rotary encoder, a 16x2 LCD, a HC-SR04 ultrasonic sensor and some LEDs.
My plan was to power this entire set up with a single 12V battery to power the 4 actuators, the 8 relay coils via JD-VCC (without the jumper) and the Arduino MEGA, with its Vin connected to the batteries positive terminal and GND pin to the negative terminal.
Would this approach be feasible? I was thinking that a typical 12V battery would drain fast when powering such a set up. Will there be a risk of the Arduino frying since it is powered at its peak allowable voltage? If I were to use the 24V actuator instead, then I cant possibly use the same battery to power the Arduino anymore. Should I use a 6V 8 Channel relay module instead? Are there other more efficient ways to do this? I am a complete beginner to Arduino and the world of electronics. Much help is appreciated!!
Sound like a 12V battery to directly power the actuators and a set of 12V relays. Then use a 12V to 5V buck converter to power the Arduino and any 5V sensors.
How often will the 240 Watt (12V 20A) actuator be running? If it's frequently, you will need a BIG battery if you want to run for long.
johnwasser:
Sound like a 12V battery to directly power the actuators and a set of 12V relays. Then use a 12V to 5V buck converter to power the Arduino and any 5V sensors.
From what I understand, buck converters step down voltage while stepping up current. I was afraid that the stepped up current would fry the Arduino and the sensors. But I also read that the electrical components only draw as much current as they need so I got alittle confused there. Is this something I should be worried about?
johnwasser:
How often will the 240 Watt (12V 20A) actuator be running? If it's frequently, you will need a BIG battery if you want to run for long.
The actuators are positional feedback actuators and will only run when if a new position is required, which for my project should only happen about 3 - 5 times in a day. the 12V 20A actuator only extend and retract over a range of 130mm (moves for 4seconds). Power is cut off when it reaches the determined position and stays in that position until a new position is required again. With that in mind, am I right to say that the maximum energy consumption of that actuator for a day is 12x20x4x5=4800J? And hence the battery required need not be too big. I was considering using LiPo Batteries.
Nanren123:
From what I understand, buck converters step down voltage while stepping up current. I was afraid that the stepped up current would fry the Arduino and the sensors. But I also read that the electrical components only draw as much current as they need so I got a little confused there. Is this something I should be worried about?
Yes, your comprehension of electricity.
In my country, we have 240 V power points rated at 10 A - ten Amps. So I plug in my Aldi LED lamp which has a power converter to provide 4 Volts at 0.75 Amps - or 3 Watts.
But does the power point force the power converter to draw 10 Amps? That would be 2400 Watts! That's an electric heater!
No, at 240 V, the power converter draws about 12.5 mA - milliAmps - or actually a little more as it wastes some power in the conversion process.
"Buck" converters - switchmode converters in general - do not "step up current", they require less current at the higher input voltage to provide the current demanded by the output device. The term "step up" is quite misleading as it implies the wrong direction of causation.
The definition is precisely the same for a transformer operating on AC.
Nanren123:
[...]about 3 - 5 times in a day. the 12V 20A actuator [...] (moves for 4seconds).
am I right to say that the maximum energy consumption of that actuator for a day is 12x20x4x5=4800J? And hence the battery required need not be too big. I was considering using LiPo Batteries.
12V*20A = 240 W = 240 J/S
5 * 4 Seconds = 20 S
240 J/S * 20 S = 4800 J per day for the big actuator.
Let's guess that everything else averages 5W
86400 second per day * 5W = 432000 WS = 432000 J
Looks like the steady drain could take two orders of magnitude more energy than moving the big actuator 20 seconds a day.
Paul__B:
"Buck" converters - switchmode converters in general - do not "step up current", they require less current at the higher input voltage to provide the current demanded by the output device. The term "step up" is quite misleading as it implies the wrong direction of causation.
I see, I understand now! Thanks! Sorry, I am still a total beginner at this.
johnwasser:
Looks like the steady drain could take two orders of magnitude more energy than moving the big actuator 20 seconds a day.
Yes, that seems to be the case. But the system will not be left running continuously throughout the day, but only about 8 hours a day. In that case, if I use a single 12V battery to power this entire system and want it to last for 2 days,
825 (using the same 5W estimate) + (452/3600)2012 = 82.7Wh
Then the capacity of the 12V battery would need to be at least 82.7/12 = 7Ah? Wait is that still considered a 'big' battery? :o
