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1  Using Arduino / General Electronics / Re: Appropriate Battery Power Source on: September 20, 2014, 01:08:45 pm
Ok, have to read into that. In the meantime, this should do it https://code.google.com/p/tinkerit/wiki/SecretVoltmeter
2  Using Arduino / General Electronics / Re: Appropriate Battery Power Source on: September 20, 2014, 07:51:19 am
What you do is use Vcc as Aref then measure the internal 1.1V reference voltage.  The rest is math.
Oh, I only saw that I can set the analog reference in Arduino, not that I could actually measure it with another AREF. Any hint? smiley


BTW, I think this does what I want. It is reasonably cheap, efficient and powerful. Only have to deal with the QFN packaging ..
http://www.ti.com/lit/ds/symlink/tps63001.pdf
3  Using Arduino / General Electronics / Re: Appropriate Battery Power Source on: September 20, 2014, 05:50:49 am
AVR chips have built-in voltage references. You could switch off all external devices and go into deep sleep when the battery reaches a certain voltage.
Oh, I see. The Arduino Reference says that the internal reference is 2.56V. Does that mean that 2.56V on n analog pin then give a read of 1023? would 5V then be a problem, if the board is also powered with that voltage?

Apart from that, I am struggling a little with "design your circuit so it runs with the voltage range of the battery" ... The ESP8266 (https://nurdspace.nl/ESP8266#Characteristics) for example doesn't seem to take the highest voltages of a LiPo.
Any suggestions how to power an ATMega/Arduino+ESP8266 with a LIPO so it can SLEEP/IDLE for at least a few month?
4  Using Arduino / General Electronics / Re: Appropriate Battery Power Source on: September 20, 2014, 04:16:57 am
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Skip the voltage regulator, use 3V batteries (e.g. 2 AA or AAA alkaline) and design all the circuitry to work with a variable voltage ranging from about 3.2 V down to 2.5 V or so. This is the industry standard practice for remote sensors, clocks, some toys, etc.

How do I implement battery control and undercharge protection in that case? I mean, I am lacking a reference voltage, don't I?
5  Using Arduino / General Electronics / Re: Appropriate Battery Power Source on: September 18, 2014, 08:59:02 am
I would get this charger over the one you linked to.
I see that one has the same chip, but separated battery/output contacts. What do they give you? A regulated voltage? Which one? Do you know at which efficiency?

EDIT: Oh, there actually was more information further down on the page smiley So a assume that is just discharge and over-current protection? That would still answer a whole lot of my questions regarding LiPo, at least if the module itself does not drain considerable amounts of power.
So these ones: http://www.aliexpress.com/item/Free-shipping-2pcs-lot-18650-rechargeable-batteries-3-7v-5800-mAh-Lithium-li-ion-battery-for/1940528115.html
and some boost IC like the LTC3525? (Though I would still like to find something that could give more current).

EDIT2: LTC3539 seems to do the trick. It is less efficient during sleep and the DFN-8 packaging is kind of impractical ...
6  Using Arduino / General Electronics / Re: Appropriate Battery Power Source on: September 18, 2014, 08:51:05 am

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I often use 3xAAA with a DC boost and USB cable (power goes in through USB port).

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But as soon as you say "sleep mode" then that method doesn't work (and neither does a standard Arduino).
What is "that method"? Your board? Or the proposed IC? The LTC3525 draws around 0.05-0.1mW when under almost no load. With 2 AA Eneloops, this would run for more than 5 years. What ius wrong with a standard Arduino? http://playground.arduino.cc/Learning/arduinoSleepCode only mentions the ineffective 7805 power regulator, but bypassing that is one of the big points of this thread.

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So, no, your "general idea" was not clear. Not really.
I am not the original poster, so it wasn't my idea anyway.

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PS: Arduinos/ATMega chips will work with a less than 5V but you must never give them more than 5V.  4 freshly charged Eneloops might give you 6V for a few minutes.
The Amtel data sheet lists a maximum voltage of 5.5V. If it is only for the first few minutes (and thus the loss is acceptable), perhaps a 5.4V Zener diode could limit the voltage during that time without being inacceptably inefficient..
7  Using Arduino / General Electronics / Re: Powering LEDs on: September 18, 2014, 06:31:06 am
Hi ! Normally how much current (mA) do I need for 1 LED to turn on ? If I give 1 A to 14 leds , will they burn ?
thanks in advance .
You seem to assume that you can easily distribute current over multiple LEDs. That is not true, however. In series, ALL the current will flow through ALL the LEDs and burn them if they are not rated for 1A. In parallel, the current may not be distributed evenly between the LEDs, due to them not being an Ohm resistor.
So if you want to drive multiple LEDs, you have to set them in series and limit the current to what ONE LED is rated for.
8  Using Arduino / General Electronics / Re: Appropriate Battery Power Source on: September 18, 2014, 06:26:20 am
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How long is a piece of string?

A truck battery + DC 5V converter will last quite a long time.

Though the question was posed inaccurate, I think the general idea was clear: In a common portable way, with easy to acquire parts. I would think this means either one or more AA batteries or or a 3.7V LiPo.

So, I do not have a good answer, but perhaps a few question and thoughts that lead us further.

Regarding AA:
- 4 Eneloop give 4.8-5.4V. Is it advisable to feed that to an Arduino 5V PIN directly? Is there an effective way (that works with Arduino sleep without draining the battery further) to get the 5.4V down? Is there an effective way to at least protect everything from the 6V of non-rechargeable batteries?
- For lower voltages, an IC is proposed in the link above, the LTC3525, however it is rated for relatively low currents. Are there stronger alternatives? 100-150mA is at least not enough for an ESP8266. I don't know about the nrf24l01 or cheap 433MHz modules.
- What are the possibilities for higher voltages?
- What is the best way to avoid decharging the rechargeable s too much?

Regarding LiPo:
- Same as above: more powerful boost ICs?
- With a LiPo, there should probably also exist a plan for recharging. can I just put this in parallel with my Arduino? http://www.aliexpress.com/item/1PC-LOT-TP4056-1A-Lipo-Battery-Charging-Board-Charger-Module-lithium-battery-DIY-Mini-USB-Port/1859868985.html
- Are the same ICs for boosting advised here?
- Same as above: decharge protection ICs?

So, what is the advised way for a compact, long lasting (that is, using sleep mode) mobile Arduino? If not anyway, what are the most beginner friendly/low quantity alternatives (for example, the module mentioned above, no SMD soldering ...)
9  Using Arduino / General Electronics / Re: What I can do with this breadboard shield? (Apprentice) on: September 16, 2014, 02:54:18 am
-Why the breadboard photo used?
We don't know why you used that photo? Perhaps to ask a question about it? Try to pose you question in Spanish, as an exception, perhaps?

-What I can look to learn from arduino?
I bought a book that I virtually never touched later. Try to think of a project, post it in Project Guidance and then read one of the many tutorials for the components you are going to use. Also, read the Arduino website, they have example setups for the most basic stuff.

You can buy such a starter kit, but the stuff in it will hit a limit very soon. I bought most of my stuff from aliexpress. It has a few weeks shipping time, but a lot of things are cheaper than shipping alone in Germany.
10  Using Arduino / General Electronics / Re: 110 V ac powering arduino on: September 13, 2014, 03:36:30 am
Yes, the voltage of the Vin Pin is regulated with a linear voltage regulator. Know, however, that this just dissipates the excessive power, so with 9V, nearly half of the power is lost there. Of course, that may not relevant, but the regulator is rated up to 1A., so it is up to 4W loss.
11  Using Arduino / General Electronics / Re: 110 V ac powering arduino on: September 11, 2014, 06:50:25 am
Have a look at these http://www.aliexpress.com/item/Free-shipping-ESP8266-serial-WIFI-AP-STA-AP-STA-coexistence-mode/2026783748.html
for Wifi access. I don't have one yet, but they look great for this purpose. I would suggest a Micro in that case, because the USB does not block the HardwareSerial that you need to communicate.

For power you could also have a look at these
http://www.aliexpress.com/item/5pcs-lot-Switched-Module-4W-800mA-Step-Down-Regulated-Power-Supplies-AC-90-240V-110-220/751818023.html
But they are not really cheaper and probably not smaller than a scrapped phone charger. These ones should contain something quite small
http://www.aliexpress.com/item/wholesale-2pcs-5V-1A-EU-Plug-USB-Power-Home-AC-Travel-Wall-Charger-Adapter-For-iphone/1999031133.html

Note that you need to supply the 5V to the 5V Pin, since the linear voltage regulator on Vin needs more then 5V (around 7?) to make 5V.
12  Using Arduino / General Electronics / Re: Can I drive an N-MOSFET with an NPN-Transistor? on: September 07, 2014, 05:15:06 am
Is this one OK for a driver chip? http://pdf.datasheetcatalog.com/datasheet_pdf/on-semiconductor/MC34151D_and_MC34151P.pdf
I can get it a little cheaper than the proposed one above and it has two independent outputs, which especially becomes interesting when switching RGB strips (then I only need two chips instead of 3).
13  Using Arduino / General Electronics / Re: Can I drive an N-MOSFET with an NPN-Transistor? on: September 07, 2014, 04:02:49 am
@Pelleput: I am not sure if I understand you correctly, but you seem to agree with my posting from September 06, 2014, 10:36:12 am (do you all see the same timestamp, or is that timezone dependent? Doesn't matter, we are in the same zone smiley)

@MarkT I did understand that. What I don't understand is how a wrong choice of the resistor can blow the MOSFET due to a high voltage:
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Consider the drain switching 100V in 100ns, and gate-drain capacitance of 50pF,
that's 50mA fed-back to the gate, which would put 28V on the gate if it was driven
through a 560 ohm resistor, causing the gate oxide to fail and the device would
explode (that's how high power MOSFETs fail).
I understand that you would NEED 28V to drain the capacitor that fast, but I don't see how it could PUT 28V anywhere, that weren't there before. And if they WHERE there before (because the gate voltage is also 100V, for example), I don't understand why they were harmfull just then.

Anyway, in general: For the IRFZ44N, V_GS,max is +-20V. V_DSS is 55V. Say I wanted to switch 50V. Would I still need to supply at least 30V on the gate for the OFF state, because else the V_GS would be higher than 20V?

Also, we are talking about 10kHz PWM and 100ns switching times all the time. The Arduino PWM is only about 500Hz. Do you think that is not enough for PWM dimming and will flicker? What would be the best way to get a higher frequency? Fiddling with the timers seems dirty ...
14  Using Arduino / General Electronics / Re: Can I drive an N-MOSFET with an NPN-Transistor? on: September 06, 2014, 03:34:34 pm
h
For a resistive load the highest power level is when the device is 1/2 switched,
so that the device gets 1/2 the load voltage at 1/2 the load current, so power =
load power / 4.   Averaged over the whole switching time the power dissipation
is a bit lower than this worst case value.
Ok, I get that. The MOSFETs resistance changes continuously between approximately infinite and approximately 0 and you estimate the dissipation with the worst case vale of R_MOSFET=R_load, where the MOSFET doesn't limit the current by orders of magnitude but still has a resistance that dissipates considerable power.

Time formula - you're charging a capacitor through a resistor, time constant t = RC,
or in terms of total gate charge(*) its  t = QR/Vgs

(*) The gate isn't an ideal capacitor at all, so the total gate charge is a more
meaningful paramemter - usually quoted in datasheets at Vgs=10V and a
large drain current.
I am still totally oblivious concerning this.  How can the switching cycle influence the current through the resistor? The circuit doesn't know when the next switching occurs. I assume it is a similar approximation as above (I am a physicist who has nothing to do with electronics professionally, so I have to derive all the practical formulas from the basics) but I didn't get it yet.
15  Using Arduino / General Electronics / Re: Can I drive an N-MOSFET with an NPN-Transistor? on: September 06, 2014, 03:32:41 pm
h
For a resistive load the highest power level is when the device is 1/2 switched,
so that the device gets 1/2 the load voltage at 1/2 the load current, so power =
load power / 4.   Averaged over the whole switching time the power dissipation
is a bit lower than this worst case value.
Ok, I get that. The MOSFETs resistance changes continuously between approximately infinite and approximately 0 and you estimate the dissipation with the worst case vale of R_MOSFET=R_load, where the MOSFET doesn't limit the current by orders of magnitude but still has a resistance that dissipates considerable power.

Time formula - you're charging a capacitor through a resistor, time constant t = RC,
or in terms of total gate charge(*) its  t = QR/Vgs

(*) The gate isn't an ideal capacitor at all, so the total gate charge is a more
meaningful paramemter - usually quoted in datasheets at Vgs=10V and a
large drain current.
I am still totally oblivious concerning this.  How can the switching cycle influence the current through the resistor? The circuit dosn't know when the next switching occurs.
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