Hi everyone,
I hope this is the right place for this question.
I am playing with an Arduino board and the power supply I’m using is a 2A 12V AC/DC converter.
The Arduino can take 7V to 20V. Therefor, I know if I use a AC/DC adapter with more than 20V I will fry the circuit.
But if I used a 10A 12V AC/DC converter will it damage the board or will the board only draw the amps required?
Reason I'm asking this is that I would like to eventually power my Arduino board directly from my car's cigarette lighter socket. I've tested the voltages and they are 12V when engine is off and 14.8V when engine is running (i.e. via the Alternator).
"The Arduino can take 7V to 20V." Read the regulator data sheet -I believe the 20V upper limit is only practicable for 12V output regulators, not 5V.
For car use, get a cigarette USB power adapter, power the board via the USB port.
The adapter is a switching regulator and will filter out any nastiness from the charging system.
jgporteous:
But if I used a 10A 12V AC/DC converter will it damage the board or will the board only draw the amps required?
Luckily for us, electronic devices only draw the amps required.
If they draw all the amps available your PC would explode when you connect it to the 10 gigawatt power station at the other end of the wire that leads to your socket.
CrossRoads:
Board will only draw the amps required.
"The Arduino can take 7V to 20V." Read the regulator data sheet -I believe the 20V upper limit is only practicable for 12V output regulators, not 5V.
For car use, get a cigarette USB power adapter, power the board via the USB port.
The adapter is a switching regulator and will filter out any nastiness from the charging system.
Thank you everyone for you advice.
What would the behavior of the Arduino board be if I ran it without the USB power adapter?
For arguments sake, let's pretend the vehicle will not spike the voltage and the voltage is 14.8V
From my understanding, there is an on-board regulator which will ensure the board's voltage will be dropped to 5V, is this true?
or, will it change the values of all my analog sensors.
I'm using an Arduino board with 2 temperature sensors, one fan and one Peltier chip (fan a Peltier are managed via Relays).
If I have to regulate the voltage to the Arduion board, I would like to build one so that the Peltier ship and fan run directly off the 14.8V.
If you can recommend a kit or circuit to build, I would really appreciate that.
There are many relay boards that will run from 5 volts, and take the digital signals from the arduino pins, and output whatever.
I would not recommend using 14.5 volts to power the arduino through the Vin. 12 volts is close to pushing it. So, as suggested, it is easy to get a cigarette plug that provides usb 5.volts.
Thanks, I will power the arduino board with 5V as suggested. I still need the 14.xV for the Load side of the relays.
The Arduino board uses 5V to open and close the relays, but the load is a separate circuit.
Because of this I would prefer a circuit to step down the voltage instead of a cigarette plug based circuit.
Any recommendations on a kit or complete product which will step down the voltage?
I have one more Q (actually I have many more but not sure what they are right now)
Someone said to me, it's the AMPs that kill you, if you have more AMPS, you are going to fry your board.
So, if my board will only take what it needs... Why does the human body get affected from higher AMPs? are we that greedy?
The answer to your question is Ohm's law: V = IR, which can be re-written as I = V/R. The human body being "greedy" is the resistance, which is only half the equation. The voltage is the other half. Human skin is fairly resistive, at least when it's not wet. This is why you can handle 12v and maybe even up to 24v supplies without really even feeling a tingle. But given a high enough voltage, a large current will be passed through you. When people say, "It's not the voltage that kills you, it's the amperage," what they mean is that a high-voltage power source won't hurt you if it is unable to pass current through you. For example, if you're standing on an insulating mat, there is no path to ground, and you can (theoretically) handle high-voltage lines with your bare hands without a problem. But if a sufficient path to ground is formed, to allow even a relatively small current to flow, then you will have problems, especially if that current passes close to or through your heart.
When we translate this to the Arduino, you say the board will only take what it "needs". This is shorthand for saying I=V/R. The Arduino has some internal resistance. This, combined with the voltage of the supply source, definitively determines the current that the Arduino will draw--that is, up to the limit of the supply source. But if you hook a peripheral up to a supply pin that has a lower resistance, it will draw more current, and that can burn out the pin, or even the microprocessor or the power supply.
joshuabardwell:
The answer to your question is Ohm's law: V = IR, which can be re-written as I = V/R. The human body being "greedy" is the resistance, which is only half the equation. The voltage is the other half. Human skin is fairly resistive, at least when it's not wet. This is why you can handle 12v and maybe even up to 24v supplies without really even feeling a tingle. But given a high enough voltage, a large current will be passed through you. When people say, "It's not the voltage that kills you, it's the amperage," what they mean is that a high-voltage power source won't hurt you if it is unable to pass current through you. For example, if you're standing on an insulating mat, there is no path to ground, and you can (theoretically) handle high-voltage lines with your bare hands without a problem. But if a sufficient path to ground is formed, to allow even a relatively small current to flow, then you will have problems, especially if that current passes close to or through your heart.
When we translate this to the Arduino, you say the board will only take what it "needs". This is shorthand for saying I=V/R. The Arduino has some internal resistance. This, combined with the voltage of the supply source, definitively determines the current that the Arduino will draw--that is, up to the limit of the supply source. But if you hook a peripheral up to a supply pin that has a lower resistance, it will draw more current, and that can burn out the pin, or even the microprocessor or the power supply.
Feel like I'm back @ school... How do I buy you and Jack a beer?
BTW, the question of whether a given amperage will hurt you directly is a separate question from whether you can be burned by the arc that is created by the electricity. You can create a strong enough arc with a typical car battery to melt metal. My brother was burned once when a metal bracelet he was wearing shorted a car battery's positive lug to a grounded piece of the frame. Welders, which you might expect to run at very high voltages, actually have a typical arc voltage around 25-30 volts. This is enough to overcome the resistance of the air and create an arc, but not high enough that it is likely to electrocute a person very readily. The key characteristic that differentiates a welder from a car battery is the welder's ability to supply a LOT of current (100+ amps). But going back to Ohm's law, with dry hands, you could grab the work clamp of a welder with one hand and the "stinger" with the other hand and probably not feel much more than a tingle. Because of the relatively high resistance of human skin, the 30 volt difference between the leads can't push enough current through you to make a difference.
Is your question like, what's the emf of a coil when you stop conduction?
I am no expert with peltier, but since they have no coils, I would think there would by no "emf" to be concerned with.
CrossRoads:
For car use, get a cigarette USB power adapter, power the board via the USB port.
The adapter is a switching regulator and will filter out any nastiness from the charging system.
BTW, heed this advice. The charging system in a car is like the wild west. 12V nominal, 12.8V average, 14.8V charging... sure. But clean DC it's not. The linear regulator will clean it up some for the downstream load, but it will be subject to a lot of abuse while it does so. Many of the precautions built into proper auto power supplies are for worst-case scenarios and an Arduino might run indefinitely with no protection. Still, it would be wise to use a supply that has been designed for that environment.
(actually I have many more but not sure what they are right now)