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I know to electronic guys this might sound a silly question, but:
What is a good way to power my N+ when I don't want to use the USB-way?
I thought about a unused car battery but a friend of mine told me I shouldn't use it. I though of using it with a 9 Volt voltage regulator (7809).
How much risk is there in going that way? A car battery has 12V and as far as I know even touching both poles shouldn't harm me because of my high body resistance.
Don't care how easy this sounds to most of you, I better ask before hurting me or my N+
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Are you trying to power it with out the board being plugged into a USB or Wall transformer (meaning battery powered)? How long does it need to run before new batteries or a re-charge?
If you take a car battery, which is rated for 12 VDC, and add it a LM7809 (or LM7808), the first questions you have to answer yourself is: how much current shall the regulator draw?
As in my case, the drop between the input and the output is 4V (9-5=4V), thus the "wasted" power is roughly 2.5W =4*0.6
Since any LM78xx has the case connected to the ground, I simply screwed the regulator to a piece of metal. The result is that the heating is almost irrelevant: I don't think it reaches 40'C.
Of sure I would add a good fuse BEFORE the regulator, as dougY said.
The regulator has several kinds of protections (thermal, short, current, etc), but if you short accidentally the battery you can have serious troubles, such as wires melting, up to battery explosion (when gets too hot).
Finally a note about the regulators: is it better a linear one or a switching one?
I believe there's a bit of confusion around this theme. It's *true* that a linear regulator is based on the heat dissipation, thus gets hot easier than a switching one. But it's also true, that a switching regulator must be designed and built very well, because it leads a *lot* of noise, when not enough filtered.
Back to my circuit, I tried two very common 5VDC adapters: one is used for a cell-phone and another for another small appliance. With none of them the circuit was working fine: the logic got crazy, the LCD displayed scrambled characters and anything seemed working. That's because I wired the adapter's output directly to the circuit, without any capacitor, inductor or else. Once I tested with the scope the "cleanness" of the +5VDC rail, it was far from being straight: lot of noise and spikes.
As soon I switched to the LM7805 everything started to working perfectly: no any error, and the +5V rail is still perfectly straight.
I wouldn't feel the linear regulators as kind of "evil".
I am just looking for a good laboratory power supply and I really want a linear one! Keep out from switching if you target experiments!
My question is not about a specific topic, I just wanted to know about it.
So, my battery has 12VDC, the drop to 9V would be 3V...
Now to the fuse: I've never used a fuse except for my car or the fuses you use for the "house electronic" (no word for that now )
Is it possible to use a normal car fuse? And they also have different Ampere-values. I think a 2-Ampere one should be right (also thinking of something like 600 mA draw normally)
Thanks for your experience-sharing about linear and switching Regulators. I already have a 7809 at home (bought it just to play around, like everything I have xD)
@Dave: Yes, I mean that I want to power it only with battery without USB.
Also, another question: Are there some cheap "wall transformers" that give me 9V to directly plug in the N+? I'm sorry, I'm still tired from going out yesterday and I don't know how the "round power connector" on the netduino is called
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The 2A fuse would be fine, but there are two kinds of fuses: the normal one and the delayed. The second one is best suited whereas a short current peak (above the nominal value) is normal: for instance a motor or even a car lamp. However, I wouldn't use a "delayed" fuse for the Netduino, because it has to react (i.e. melt) sooner and it doesn't have reasons for current peaks.
Markus, just a note about the car battery.
I mean to use it as "off from the car", not during the car is running or -even worse- when the ignitor is on. In such a condition the battery voltage is somewhat a nightmare, with ton of skipes, noise and the voltage can fall even below 6V for a brief.
If you're going to use the Netduino for any "automotive" application, the adapter must be much more complex.
I mean to use it as "off from the car", not during the car is running or -even worse- when the ignitor is on.
Thats not my plan, but thanks for the advise
Ok, so I have to get a "non-delayed fuse".
Ok, and here comes the next question to my mind: Would it be a bad idea to run not only the N+ from my battery, but also other electric loads? Because if I go the car battery way, I would have to possibility to drive for example a servo with 12V or 9V.
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The reason I asked about how long you want it to run before recharge is that I am using a 2700mAh LiPoly Battery with a Lipo Charger and a Booster from Adafruit and Sparkfun. I can run Pandora's Box which has 6 sensors as well as a back lit LCD screen for 12 hours before recharge. It's one idea as long as you don't have to power any motors, solenoids and the like.
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I thought about the car battery because it delivers 12V, so I can do both, power other things AND the N+.
What do you mean with "Booster"?
Opto-Isolating sounds good, I have to look into it, I have nothing at home for this =)
Greets
LiPoly Batteries are only 3.7v so they are not enough to power a ND. The booster takes the 3.7 and turns it into 5v for the ND. https://www.sparkfun.com/products/8290
LiPoly Batteries are only 3.7v so they are not enough to power a ND. The booster takes the 3.7 and turns it into 5v for the ND. https://www.sparkfun.com/products/8290
There is something like that? The beauty of technic
But are there any "cons" on it, so does it draw more current, does it get hot or something like that?
If you need help with NeonMika.Webserver, please just leave a note in the thread and/or contact me via Skype
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--- Mistakes teach you important lessons. Every time you make one, you are one step closer to your goal. ----
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If you need help with NeonMika.Webserver, please just leave a note in the thread and/or contact me via Skype
-----------------------------------------------------------------------------------------------------------------------------------------------------------------------
--- Mistakes teach you important lessons. Every time you make one, you are one step closer to your goal. ----
-----------------------------------------------------------------------------------------------------------------------------------------------------------------------
There is something like that? The beauty of technic
But are there any "cons" on it, so does it draw more current, does it get hot or something like that?
Greets, Markus
Yes, Current is a concern. Max of 300ma. The first prototype of Pandora's Box had 2 additional sensors and I did melt the Step-up (Booster). Now with the setup I am running it doesn't get hot at all.
Yes, Current is a concern. Max of 300ma. The first prototype of Pandora's Box had 2 additional sensors and I did melt the Step-up (Booster). Now with the setup I am running it doesn't get hot at all.
Doesn't the N+ alone consume about 200mA or something like that?
I've no idea
And Mark, thanks for the post, I will have a look at it.
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--- Mistakes teach you important lessons. Every time you make one, you are one step closer to your goal. ----
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Doesn't the N+ alone consume about 200mA or something like that?
I've no idea
And Mark, thanks for the post, I will have a look at it.
Greets, Markus
I think it's closer to 100-125ma. I haven't run a full test on the system to see but this thing has run 100s of hours on the battery with no melt downs and no sensor failures due to power issues.