17 replies to this topic

[Ben Harel]

Hi! I purchased a Netduino Plus. What do I need to buy in order to power it?(Not the pc cable). Also, how do I connect a battery to it? Thank you!

[Paul Newton]

Hi Ben,

Welcome to the forums!

Obviously you can power it via USB from a PC.
But, you might not have considered that you can also power it from a 5V USB wall adapter, an in-car adapter, or a rechargeable USB gadget charger.
In fact with my current robot, I power my Netduino Plus using one of these: USB Emergency charger. Its small enough to fit on the robot and seems to last for ages. I use a separate 9V battery pack (6 x AA) for the motors.

As with other ways of powering the Netduino, the 5V and regulated 3.3V outputs are available on the 5V and 3.3V pins. These can be used to supply power to other shields or bread board circuits.

Sticking with a 5V input, you can also supply power into the 5V pin on the Netduino. This might be useful if you want to connect your 5V power from another shield, or via flying leads from a 5V supply.

Moving away from 5V, the Netduino has a 5V regulator built in. So you can also apply power via the barrel connector which should be between 7V and 12V. The barrel connector is connected internally to the Gnd and Vin pins, so you can input/output (7V - 12V) power via them also. If you do go this way, it is probably going to be because you have a higher voltage (than 5V) for driving some hardware - relays or motors maybe.

You should note that the higher the voltage on the Vin pin, the more "work" the onboard 5V regulator has to do. So if you use the maximum 12V, it is not a good idea to try and take lots of current from the 5V output and GPIOs - if you do, the regulator will get hot. When things get hot, the smoke (that makes all electronics work) tends to escape leaving your hardware late - that's late as in "this is my late Netduino board".

I have not mentioned anything about the limits of what you can take from the Netduinos, go and have a look at the hardware page, and the Wiki and you should find everything you need to know.

One last thing, if you are driving items like motors, you may find it best to use separate battery packs. When using a single 9V battery pack, I found that every time my motors spun up, my Netduino Plus rebooted.

Hope this gets you started - Paul

[CharlesTucker]

Hello, thanks for the great explanation. It leaves me with one question (actually I found your answer when trying to find an answer to my question). You mention that if powering the Netduino from an external 12V source, it is not a good idea to try and take lots of current from the 5V output. I can imagine that, but the question I had, and could not find the answer (I guess I did not search good enough), is what is considered "a lot of current". Just to be sure, I am talking about the 5V output only. Best regards, Peter

[carb]

Hello, thanks for the great explanation. It leaves me with one question (actually I found your answer when trying to find an answer to my question). You mention that if powering the Netduino from an external 12V source, it is not a good idea to try and take lots of current from the 5V output. I can imagine that, but the question I had, and could not find the answer (I guess I did not search good enough), is what is considered "a lot of current". Just to be sure, I am talking about the 5V output only.

Best regards, Peter

Peter,

800 milli amps is the maximum for the both the 3.3 vdc and 5 vdc regulators.

You can verify that by looking at the schematic drawing on the hardware page for the Netduino Plus, the drawing gives the part numbers for the regulator chips. In this case, MC33269DT-5.0G and MC33269DT-3.3G.

Then google will show the data sheets for these regulators.

A good rule of thumb is if the regulator is hot to touch you are drawing to much current from it or you don't have a good enough heat sink on it to disipate the heat. Also the higher the input voltage, the more heat that will need to be disapated. A 12 vdc input will cause more heat than a 9 vdc input for the same load on the output of the 5 vdc regulator.

Hope this helps,
Chuck

[CharlesTucker]

Hi Chuck, yes, this helps a lot, I now have a clear answer to my question, as well as a good explanation of how I could have found it myself, thanks a lot

[Paul Newton]

Remember that the 5V and 3V regulators are in series. All the current used at a voltage of 3.3V passes through the 5V regulator and counts towards the 800mA limit of the 5V regulator. Paul

[Gutworks]

Hi Ben, and welcome to the wonderful world of Netduino and microelectronics!

One point I would like to clarify regarding the external 7-12V power supply is that by just plugging in your power supply without anything connected to the Netduino will not overheat the regulator. The current, measured in Amperes (A), is provided by a supply and demand principal; current will only be provided as it is needed. Each power supply will have a the maximum current rating printed on it's label, and the amount can vary a lot from each power supply. For instance I have 12V power supplies that have a maximum capability of 0.2A (200mA) and others up to 2A. As you connect devices to your Netduino each will attempt to draw as much current as it needs from your Netduino and so you have to be careful not to draw more than the Netduino is rated.

Two things to consider when connecting devices to your Netduino is that each GPIO pin has a limited amount of current they can supply, and the overall Netduino has a maximum limit that when you add up all the amps each device will use, should not exceed that limit without risk of damage.

For the Netduino and the Netduino Plus those limits are as follows:

max current: 8 mA per pin
digital pins 2, 3, 7: 16 mA per pin
analog pins 0-3: 2 mA per pin
microcontroller max current: 200 mA total

With that said, I have found the Netduino to be incredibly robust and able to stand up to a lot of abuse, which is great for error prone people like myself. However to limit that risk I tend to use power supplies that provide under 500mA (0.5A). If I have devices that require more amps then I use a separate supply to power them.

The Forums here are a great place to learn, with many experienced people like Paul and Chuck willing to share their vast knowledge. I've learned so much from reading the posts here and asking my own questions. Generally, the community is very quick to respond and help a fellow Netduino enthusiast learn and join in with all the fun.

Cheers,
Steve

[boez52]

I am using the netduino plus for a school project. My problem is that the backup power supply (8 AA battery pack) voltage goes down when connected to the netduino. The battery pack voltage would be 10V but when the battery pack is connected to the netduino the voltage drops to 8V and continues to drop as the batteries discharge. This would cause the netduino to lose power before the batteries are anywhere near fully discharged. I thought the netduino would regulate the battery voltage via the barrel jack, is this not true? Or do I need to add a voltage regulator before plugging the power to the netduino?

[Chris Walker]

Hi boez52,

I am using the netduino plus for a school project. My problem is that the backup power supply (8 AA battery pack) voltage goes down when connected to the netduino. The battery pack voltage would be 10V but when the battery pack is connected to the netduino the voltage drops to 8V and continues to drop as the batteries discharge. This would cause the netduino to lose power before the batteries are anywhere near fully discharged. I thought the netduino would regulate the battery voltage via the barrel jack, is this not true? Or do I need to add a voltage regulator before plugging the power to the netduino?

The power barrel jack will regulate your voltage down to 5V (and then to 3.3V). But it's not going to be able to do so when the power drops much beyond 7.5V.

If you want to hook it up directly to a 5V LDO regulator (or step-down converter) and then supply that to the 5V header, you'll get more juice out of your batteries.

Chris

[CW2]

My problem is that the backup power supply (8 AA battery pack) voltage goes down when connected to the netduino. The battery pack voltage would be 10V but when the battery pack is connected to the netduino the voltage drops to 8V and continues to drop as the batteries discharge.

How exactly do you have the batteries connected? What other devices are connected to Netduino, if any? From your description it sounds like the batteries are discharged very quickly, which can be caused by a short circuit or there is a device that draws too much current.

[boez52]

Hi boez52,


The power barrel jack will regulate your voltage down to 5V (and then to 3.3V). But it's not going to be able to do so when the power drops much beyond 7.5V.

If you want to hook it up directly to a 5V LDO regulator (or step-down converter) and then supply that to the 5V header, you'll get more juice out of your batteries.

Chris

The batteries are at most 11.2V (5400mAH) when plugged in the netduino via the barrel jack. The netduino is pulling around 150mA. Nothing else is connected the netduino. The batteries should last more than 24hrs but I can only get around 10hrs out of them. Are you saying I should plug the batteries in a 5V regulator then the 5V regulator to the 5V pin on the netduino? If so will the 7805 regulator work? The batteries should drop from 11.2V and reach an equilibrium voltage of 9.6V for majority of their discharge.

[boez52]

How exactly do you have the batteries connected? What other devices are connected to Netduino, if any? From your description it sounds like the batteries are discharged very quickly, which can be caused by a short circuit or there is a device that draws too much current.

The batteries are in series with a capacity of 5400mAH. Nothing is connected to the board but a LCD and some thermistors. I measured the current of the whole system and it draws 150mA. The batteries should last for more than 24hrs but I only get 10hrs.

[CW2]

The batteries are in series with a capacity of 5400mAH....The batteries should last for more than 24hrs but I only get 10hrs.

Could you share the battery type (to get its discharge curve)?

[boez52]

NiMH

[boez52]

Could you share the battery type (to get its discharge curve)?

NiMH

[CW2]

Ok, I meant the battery name/type, although the chemistry is also helpful. Just for verification, is it really 5400 mAh? Because I could not find any NiMH AA cell with such capacity, they are usually less than 3000 mAh; also from your measurement 150 mA * 10 h = 1500 mAh, which seems more likely.

[boez52]

Ok, I meant the battery name/type, although the chemistry is also helpful. Just for verification, is it really 5400 mAh? Because I could not find any NiMH AA cell with such capacity, they are usually less than 3000 mAh; also from your measurement 150 mA * 10 h = 1500 mAh, which seems more likely.

They are AAs by Sanyo with a capacity of 2700mAH... I have two packs of 8 cells. The two packs are each in series with a diode then the diodes come together to the same node to create a diode-or.

[CW2]

They are AAs by Sanyo with a capacity of 2700mAH... I have two packs of 8 cells. The two packs are each in series with a diode then the diodes come together to the same node to create a diode-or.

Hm, the Sanyo batteries have rather good discharge characteristic (HR-3U datasheet, pdf), they should provide more than 2000 mAh under 540 mA load before the voltage drops below 1.2V (nominal). Also, 9.6V (minus the diode voltage drop) is still well above the minimum required by the Netduino voltage regulator (V_DROP ~ 1 V @ I_OUT < 500 mA), so I am not sure why you are not getting ~2200 mAh * 2 / 150 mA = ~30 h of run time. The only explanation that comes in my mind at the moment is that the circuit consumes more current (network activity, LED backlight?) or the batteries do not have the advertised capacity (*).

(*) I am not an expert in this field, but certain high-capacity NiMH cells are known to degrade relatively quickly due to their high self-discharge rate, some people prefer using lower-capacity cells instead, or low self-discharge ones (Sanyo Eneloop, GP ReCyko).