How to not fry my Arduino [Power connection] - Page 1
Forum section: electronics / projects

author: lion
author_rank: Contributor
timestamp: May 13, 2017, 03:58:27 pm
content: Is this well connected? I dont want to fry my Arduino Voltage regulator (800mA).I wan't to feed the other stuff in the project from the 5V Power supply.

author: igendel
author_rank: Frequent Contributor
timestamp: May 13, 2017, 04:06:40 pm
content: It's not clear whether the bottom power supply gives 8V or 5V...

author: lion
author_rank: Contributor
timestamp: May 13, 2017, 04:10:13 pm
content: Typo, I edited

author: igendel
author_rank: Frequent Contributor
timestamp: May 13, 2017, 04:26:47 pm
content: ok. Basically, Arduinos take as much power as they need, so as long as the voltage is in the correct range, the power supply's maximum current *should* be higher than what your system needs.You should be very careful, though, with how much power your Arduino passes on. For instance, if you try to power a motor directly from the output pins, or too many LEDs at once, the components will fail.

author: Pack34
author_rank: Frequent Contributor
timestamp: May 13, 2017, 04:28:11 pm
content: Why aren't you powering everything off of 5V?

author: lion
author_rank: Contributor
timestamp: May 13, 2017, 04:29:48 pm
content: Quote from: Pack34 on May 13, 2017, 04:28:11 pmArduino isnt stable at 5V. Recommended voltage is from 7-12VDC

author: Boschi
author_rank: Regular Contributor
timestamp: May 13, 2017, 04:30:46 pm
content: other than that you can use the same 5V power supply for both the arduino and the SIM800, instead of connecting the supply through the power jack of the mega you just need to connect it through the 5v input pin.also if you really want to push 800mA through the arduino 8V are too much. usually the voltage regulator is rated for 1W, but you are tring to push 0.8 * (8-5) = 2,4W

author: lion
author_rank: Contributor
timestamp: May 13, 2017, 04:38:38 pm
content: Quote from: Boschi on May 13, 2017, 04:30:46 pmDo you have any circuit explaining how to do that? The thing is I have other things to power (LCD, 8 relay's,...)

author: igendel
author_rank: Frequent Contributor
timestamp: May 13, 2017, 04:40:24 pm
content: Quote from: Boschi on May 13, 2017, 04:30:46 pmTrue. If you can make sure the connection is stable (physically), this will be easier and more efficient.

author: Boschi
author_rank: Regular Contributor
timestamp: May 13, 2017, 04:55:41 pm
content: Quote from: lion on May 13, 2017, 04:38:38 pmjust stick the 5V of the PSU in the 5V pin of the boardremember that you can pull just 40mA for each pin, and the total current draw from all the pins should be lower than 200mA.

author: lion
author_rank: Contributor
timestamp: May 13, 2017, 05:03:41 pm
content: Quote from: Boschi on May 13, 2017, 04:55:41 pmMy only problem is the GSM. It has 800mA! I connect the GSM to what?

author: Boschi
author_rank: Regular Contributor
timestamp: May 13, 2017, 05:16:38 pm
content: keep calm, i was referring to the arduino and the relays. are you driving them directly from an arduino pin? if so this could be a problem.about the SIM module, it draws is current directly from the PSU, so no problem here

author: tablatronix
author_rank: Regular Contributor
timestamp: May 13, 2017, 05:20:18 pm
content: Can you not bypass the regulator on the mega for 5v , is there not a 5v in outside of the usb connector ? Sounds like the only reason external 7v+ is suggested is because of the voltage drop of the regulator on the power jack.It should run ok on 5v provided it is high enough and no voltage drop or long wires, say 5.2 v etc.

author: lion
author_rank: Contributor
timestamp: May 13, 2017, 05:26:10 pm
content: Quote from: Boschi on May 13, 2017, 05:16:38 pmYes, the LCD and the relays are from an arduino PIN.

author: Rick Law
author_rank: Super Contributor
timestamp: May 13, 2017, 05:32:17 pm
content: Quote from: lion on May 13, 2017, 03:58:27 pmLion,Are you sure your SIM800L-GSM runs off 5V? From what I've seen,SIM800L-GSM is a 3.3V to 4.2V module. Unless your version of SIM800L is different and runs off 5V, you can burn it out.There is a 3.3V out with the Arduino UNO/Nano, but at 50mA or less, it is not enough current to run the SIM800L. Not sure about how much the Arduino Mega can supply.Check this link (warning) here::http://www.ayomaonline.com/programming/quickstart-sim800-sim800l-with-arduino/and here:https://exploreembedded.com/wiki/GSM_SIM800L_Sheild_with_ArduinoRick

author: lion
author_rank: Contributor
timestamp: May 13, 2017, 05:33:30 pm
content: Quote from: tablatronix on May 13, 2017, 05:20:18 pmMy issue here is the current, not the voltage. If my GSM has 800mA it fries the voltage regulator.The GSM doesnt work with the USB port. It needs more current.

author: lion
author_rank: Contributor
timestamp: May 13, 2017, 05:35:16 pm
content: Quote from: Rick Law on May 13, 2017, 05:32:17 pmMine is this one Rick:I guess it has some voltage regulator inside to drop it down.

author: Rick Law
author_rank: Super Contributor
timestamp: May 13, 2017, 05:43:04 pm
content: Quote from: lion on May 13, 2017, 05:33:30 pmYeah, looks like you have the 5V one (in link1 above) that is suppose to have additional regulator.

author: Pack34
author_rank: Frequent Contributor
timestamp: May 13, 2017, 05:51:41 pm
content: Quote from: lion on May 13, 2017, 04:29:48 pmIt's a 5V system. Just supply 5V to the internal power rail and not through the regulator. You'll be fine.

author: lion
author_rank: Contributor
timestamp: May 13, 2017, 06:31:48 pm
content: Quote from: Pack34 on May 13, 2017, 05:51:41 pmIs this good?

author: rdl
author_rank: Super Contributor
timestamp: May 13, 2017, 06:56:47 pm
content: Check to be sure, but using a 5 volt power supply you probably want to connect it to the 5v input on the Arduino, not to V in. I don't use Arduino, but on these type of devices Vin is usually to the onboard regulator while 5V will connect to the actual power rail.

author: alsetalokin4017
author_rank: Super Contributor
timestamp: May 13, 2017, 07:41:06 pm
content: Correct.Quotehttps://www.arduino.cc/en/main/arduinoBoardUnoBut if you know your 5v supply is well regulated and stable, you can power the Arduino through the 5v pin. At your own risk, of course.

author: mariush
author_rank: Super Contributor
timestamp: May 13, 2017, 08:33:10 pm
content: You should first make sure that the power adapter you use can actually supply 2A at 5v.A lot of cheaper adapters lie and when you take so much current from them, the voltage will go down, if you test that adapter you may find out it outputs 4.7v at 2A or something like that.The easiest way to check how well your power adapter works would be to simply use a multimeter to measure the voltage while you connect something to it that uses power. For example, get a piece of insulated wire and measure the resistance with a multimeter and then you can figure how much current the wire would consume using the simple formula V = I x R (voltage equals current times resistance) ... or if we rearrange this, current = voltage / resistance.So for example, let's say you have a few meters of some kind of insulated wire , you set the multimeter on resistance measurement and touch the leads together to measure the multimeter leads resistance and press the REL button on the multimeter if it has one to substract the meter leads resistance (or memorize and substract value after reading) and then you measure the resistance of the wire.Let's say the resistance of this length of wire is 0.5 ohm .. then you know if you connect the wire between 5v and ground, the wire should consume 5v / 0.5 ohm = 10 watts or 2A (5v x 2A = 10 watts)To prevent the wire from burning up, you should put it in a cup of cold water (add some ice)...So when you have the wire connected and you know there's some amount of power burning up in the wire, you can use the multimeter to measure the voltage and you'll know the voltage the power adapter can supply at that amount of power consumption.The arduino boards have a DC In barrel jack connectors which accept a wide range of voltages. From there, the input voltage goes into a linear regulator which produces 5v that goes to the microcontroller.The exact type of linear regulator varies from one arduino model to another but in essence they work about the same : in order to output the desired voltage, the input voltage must be higher by some amount which depends on the regulator type, how much current the whole board demands, how hot the linear regulator is and other things.For the most commonly used 1117 linear regulator, such a linear regulator can usually output up to 0.8A if it's sufficiently cooled (I wouldn't design boards where all the stuff connected to the board uses more than maximum 0.5A based on the chip and how well i believe it can cool itself using the circuit board) and could require as little as around 0.6v if the whole board uses let's say less than 100mA , and up to 1v if you're getting close to 0.5a..0.8a of current.Other linear regulators are designed to output less current (let's say maximum 0.25A) but don't need an input voltage that much higher compared to the output voltage. Some require as little as 0.1v above the output voltage to output the desired voltage.Anyway, this is basically the reason why the Arduino guys say you can power the board with 7v .. 12v , because they're using a linear regulator that needs 5v + 0.6v ..1v to output 5v, and because they know power adapters can have varying degrees of quality they just play it safe and say you need at least 7v.An important thing to note... most linear regulators will not shut down if the input voltage is too low to be able to output the desired voltage, but they'll simply do their best to get the output voltage as close as possible to the desired voltage.So for example, if you put 5v on the DC In jack, the linear regulator will most likely work but the output will be around 4.3v ... 4.5vArduino chips can work with a wide range of input voltages, they don't necessarily need exactly 5v to work, but they do require some minimum voltage levels in order to reach some frequencies. So for example, if your arduino has a 16 Mhz oscillator and is designed to run at 16 Mhz, that could mean the chip needs at least 4.5v in order to be stable at that frequency.If you don't need all that speed, in theory you could change the oscillator to a 8 Mhz or 12 Mhz one and change the frequency in software, and that may allow you to run the Arduino board with as little as 3.3v or 3.6vAs others have explained, your arduino most likely has the pins to go around the linear regulator and power the chip on the board directly with 5v through two of those pins. If you decide to power your board like that, it wouldn't hurt to connect an additional capacitor as close as possible to those pins, I'm thinking something like 100uF or more with a voltage rating of 10v or higher.Why would this help... imagine that your power adapter is a bit slow to react to changes in power consumption. So when your GPS suddenly starts "talking" to the network and demands up to 800mA from the power adapter, the power adapter may be slow to react and then for a few milliseconds the voltage would go down below 5v. If the voltage goes down too much before the power adapter reacts and pushed more power through the wires, the arduino chip may reset itself or may lock and you'd have to disconnect and reconnect the power to get it working.The GPS board already has those capacitors on it, and the Arduino board should have a capacitor as well, but adding an extra capacitor shouldn't hurt and they're cheapAnother thing to keep in mind ... most I/O pins on an Arduino can't output a lot of power on them, most would be limited to maximum 15-25 mA or something like that. So for example, you shouldn't power a 5v relay directly from the Arduino board, you should connect an npn transistor or a mosfet to the I/O pin (with a resistor in series for protection) and then your Arduino uses only around 1-5mA to turn on the transistor or mosfet (both act as power switches) and then the parts connect the relays directly to your 5v adapter.You should find plenty of tutorials out there on the Internet which teach you this.