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Topic: Power suply for Arduino Yun (Read 3187 times) previous topic - next topic

aabm01

Jan 21, 2016, 04:16 pm Last Edit: Jan 21, 2016, 04:31 pm by aabm01
Hi

I want to power the arduino Yun through the VIN pin, because the Arduino will be in a box with a custom PCB with sensors.

I have read in the Arduino Yun Overview that if I want to use the VIN pin, I must supply a regulated 5VDC because there is no on-board voltage regulator for higher voltages, which will damage the board.

I have found this power supply Mean well R-15-5. I am not sure if it'd be appropriate to power the arduino Yun because in the specifications says:

Protection overload --> Above 105% rated output power (Protection type : Hiccup mode, recovers automatically after fault condition is removed)
Protection over voltage -->  5.75 ~ 6.75V (Protection type : Shut off o/p voltage, clamping by zener diode)

  • In the Protection over voltage,  5.75 ~ 6.75V means that the voltage can arrive until 6.75V? In this case, the Yun could be damaged?
  • The fact that the voltage of the power supply is 5V and the current 3A is Ok for the Yun?
  • The fact to insert the power supply together with the Yun and a PCB with sensors in a box can affect the normal work of the arduino or the sensors?

Thanks

Toni

ShapeShifter

I'm not a power supply expert, but I don't see anything in those specifications that scares me. If I got something here wrong, I'm sure someone will be along soon to correct me.

The way I understand it:
  • The "protection overload" is to protect the power supply if you try to draw too much current from it. At 105% of the rated load (3.15 Amps) it will automatically shut down the power supply. It will then "hiccup" and briefly turn on periodically to see if the overload is still there - if so, it shuts down again. Once the overload is gone, the "hiccup" will sense that, and turn the supply back on again.
  • The "protection over voltage" is an additional protection stage in the power supply. If something fails in the regulation circuitry fails, and the output voltage rises, there is an additional zener diode that will clamp the output to around 5.75 to 6.75 volts.

The output is still regulated to +/- 2% (4.9V to 5.1V) at a maximum of 3 amps. The protection features are just a backup to help prevent problems in case something goes wrong. If the regulator in the power supply fails, it's possible that the Yun could see up to 6.75 volts before the supply shuts down. I suppose it's possible that there could be some damage to the Yun, but you're already experiencing a system failure at that point.

The biggest concern I have is that the supply is very much overkill for the Yun - half an Amp is more than enough to drive the Yun. Do your sensors really draw 2.5 Amps? That could be a lot of heat and power dissipation for an enclosed box.


aabm01

Thanks for your answer.

The sensors are the MPXV7002 they only need 5V and 10mA. The fact of this power supply is because I can't find another one with an output for example 5V and 1A.

I am not electronic either, but I think that the fact that the amperage of the power supply is 3A, means that is the maximum amperage that it can supply, but it isn't going to damage the Yun because the arduino is only taken the amperage that he needs to work.

I am not sure but I think that in the regulated power supplies or transformers the voltage practically don't changes unless consumption reach the limit  current marked by design (which is somewhat higher than nominal). Perhaps a source of 3 A does not cut until it reaches 3.5 A. So, they can supply only  the amperage that the Yun need with 5V.

So, I understand that if the arduino takes 40mA and the power supply can give 3A, the power supply is working under his real capacity so he hasn't to emit heat.

But as I said I am not an expert and it would nice to know if it can be a real problem.

sonnyyu

#3
Jan 22, 2016, 03:33 pm Last Edit: Jan 22, 2016, 03:34 pm by sonnyyu
Mean well R-15-5:


Ripple & Noise: 80mVp-p  is bit of too high for this appliaction

Apple iPhone:


Samsung oblong



http://www.righto.com/2012/10/a-dozen-usb-chargers-in-lab-apple-is.html


I vote SQLite even half awake half sleep since Google & Apple does:

  • Google & Apple engineers has higher IQ than industry average
  • Google & Apple engineers get higher pay than industry average
  • Google & Apple has more resource





I vote Apple iPhone power adapter here.



aabm01

Thanks

That would be an option but as I mentioned, everything is placed inside a box, and installed in machines placed in industrial companies, so the USB chargers would very easy to steal or unplugged. That's the reason because I want a iternal power supply.

The fact is that isn't easy to find one with specifications similar to the USB chargers.

CrossRoads

Designing & building electrical circuits for over 25 years.  Screw Shield for Mega/Due/Uno,  Bobuino with ATMega1284P, & other '328P & '1284P creations & offerings at  my website.

sonnyyu

#6
Jan 22, 2016, 04:41 pm Last Edit: Jan 22, 2016, 04:42 pm by sonnyyu
Thanks

That would be an option but as I mentioned, everything is placed inside a box, and installed in machines placed in industrial companies, so the USB chargers would very easy to steal or unplugged. That's the reason because I want a iternal power supply.

The fact is that isn't easy to find one with specifications similar to the USB chargers.
Work around:

Get empty housing



put Apple USB chargers into.






sonnyyu

Iphone AC Adaptor Diagram:





The key element to reduce Ripple & Noise is Pi LC Filter, C9, C16, L3, C14.

Use Pi LC Filter for Mean well R-15-5 or  CrossRoads' recommendation?






ShapeShifter

I vote Apple iPhone power adapter here.
Just be aware that there there are a lot of counterfeit clones out there that look the same, but don't have nearly the same performance as the genuine Apple adapter.

The 80 mV ripple doesn't bother me too much, it's 1.6% of the output voltage, and less than the 2% regulation specification. If the ripple worries you, add an output filter capacitor - put it on the custom board near the VIN pin. The module CrossRoads recommends has double the ripple on the output (150 mV.)

Or, if this is going into an industrial machine, does it have a 24 VDC supply (fairly common) that you can tap into? In that case, bring 24V onto your custom board and use a DC to DC converter. I've had good luck with THIS ONE which gives less than 25 mV ripple and accepts up to 36 VDC input, with a 1.5 Amp output.

aabm01

Hi.

CrossRoads thanks for the link that could be an alternative. I have a question. Why I have to wire up the incoming AC with a fuse? This converters don't have all the protections needed to get the correct output?.

sonnyyu thanks for the advise but if I can get a power supply that accomplish the requeriments will be better, so maintaining the circuit simple.

ShapeShifter I have no the posibility to connect to 24VDC (only 220 or 380 AC), but I think I am going to try the Mean well R-15-5. and see if the values from the sensors are correct.

Thanks

CrossRoads

Anytime you are connecting to a Mains line you should use some kind of fuse for protection.
It's called out in the datasheet also.
Designing & building electrical circuits for over 25 years.  Screw Shield for Mega/Due/Uno,  Bobuino with ATMega1284P, & other '328P & '1284P creations & offerings at  my website.

ShapeShifter

To expand on CrossRoads' comment: the fuse isn't there to assure proper output, it's there to help prevent a fire or melted line cord wires if there is a short or overload inside the power supply. It's a very good idea.

A typical way to handle the fusing is to use an AC Power Entry Module. This is a panel mount device that goes on the enclosure, and not only serves to pass power into the enclosure, but usually has a fuse, power switch, and often power line filters. They typically have a standard socket for a line cord, and screw or FastOn tabs inside to make it easy to run wires from the power entry module to your power supply.

Here's one that does it all - cord socket, fuse, switch, and filter, with guick-connect FastOn tabs for the internal connection:



Keep in mind that the Mean Well supply you're looking at is a component, not a finished power supply system. Unlike wall-wart supplies, or power supply bricks, it's just one part of a finished system. It is still your responsibility to enclose it properly, provide proper wiring and fusing, and prevent accidental contact with the supply conductors.

sonnyyu

#12
Jan 25, 2016, 06:44 pm Last Edit: Jan 25, 2016, 06:46 pm by sonnyyu
...
Keep in mind that the Mean Well supply you're looking at is a component, not a finished power supply system. Unlike wall-wart supplies, or power supply bricks, it's just one part of a finished system. It is still your responsibility to enclose it properly, provide proper wiring and fusing, and prevent accidental contact with the supply conductors.
Typical Mean-Well Forward circuit:



FS1 (Fuse), a device used in electrical systems to protect against excessive current

Inrush Current Limiting - RTH1 (thermistor) suppresses the inrush current during cold
start. Thermistor is a resistor whose resistance changes in indirect proportion to
temperature, which is why it is called a NTC (Negative Temperature Coefficient)
Thermistor. At cold start, the high resistance suppresses inrush current; after starting up
for a while, the resistance decreases to reduce power consumption in normal operation.

Anti-Lightning Surge - ZNR1 (transient/surge absorber) is a resistive component. Part
number 471, commonly used in Mean-Well products, it possesses high resistance at normal
condition. As the voltage across it increases, its conductivity also increases; the
resistance decreases greatly when the voltage across it reaches 470VDC or 332VAC,
and the conductive current is around 1mA. With that characteristic, the transient/surge
absorber is able to bypass the abnormal surge voltage so as to effectively inhibit the
surge voltage from entering the S.P.S.


Mean Well USER Technical Manual




sonnyyu

#13
Jan 25, 2016, 07:04 pm Last Edit: Jan 25, 2016, 07:05 pm by sonnyyu
...
The 80 mV ripple doesn't bother me too much, it's 1.6% of the output voltage, and less than the 2% regulation specification. If the ripple worries you, add an output filter capacitor - put it on the custom board near the VIN pin. The module CrossRoads recommends has double the ripple on the output (150 mV.)
...
The PSRR is defined as the ratio of the change in supply voltage in the op-amp to the equivalent (differential) output voltage it produces



https://en.wikipedia.org/wiki/Power_supply_rejection_ratio

Linear Regulated Power Supplies could have very good Ripple & Noise rating as low as  ~0.08mV. It will be used at high sensitivity sensor circuit.






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