7 replies to this topic

[embarus]

Hello everyone I buy this adapter from seeedstudio http://www.seeedstud...l?cPath=178_181 and not aware if it compatible with Netdino Plus. When I got both devices I see 7.5 - 12 V. for adapter plug on Netduion Plus. So may I use this adapter with Netduino Plus or it can damage circuit. If it does not work Netduino, please suggest me the best compatible one that can buy from internet. Lastly, how many currency mA best for Adapter to connect with Netduino plus sine it does not show on board ( show only 7.5 - 12 V.) Thank you and hope I can share my Netduino Project from Thailand.

[Paul Newton]

Hi Embarus,

If you have not already paid for the power supply, look for another one that has 7.5V output or 5V output. (7.5V would be connected to the barrel connector, 5V can be connected directly to the Vin pin.)

If you have already got it:

1/ Check that the output has + in the centre and - on the outside. There is a picture on the base of the adapter in the link you gave, but I can't quite see it.
You want:


2/ Try it.
As long as the polarity is correct you will not damage the Netduino.
You may find it is not as reliable as it should be, but I think it will probably work.

The current required for the Netduino depends on the devices you have connected to it.
The maximum current that the regulator can handle is 800mA see Wiki page. So the input current should always be less than this. If the Netduino is using more than 800mA the Netduino will probably be damaged.
The power supply you chose should be rated to give more current than the current the Netduino uses.
So if you are going to use 800mA, buy a 1 Amp power supply.

Hope this helps - Paul

[Stefan]

To be honest, I've used a 5V power supply, without problems. But without guarantees!

[embarus]

Hi Paul Newton, thank you very much for your useful and very complete information. I feel warm welcome to this community. and hope I can contribute to this community. Also, thank Stefan for letting me know that you uses 5v adapter.

[Gorf]

...The current required for the Netduino depends on the devices you have connected to it.
The maximum current that the regulator can handle is 800mA see Wiki page. So the input current should always be less than this. If the Netduino is using more than 800mA the Netduino will probably be damaged.
The power supply you chose should be rated to give more current than the current the Netduino uses.
So if you are going to use 800mA, buy a 1 Amp power supply.

This bit has confused me (easily done, I'm afraid).

The first paragraph seems to be contradicted by the second.

In the first, it looks to me like you're saying that the ND will attempt to draw as much current as is needed by all the attached peripherals, but it might be damaged if that goes over 800mA. Then in the second you say that you should oversupply if you're going to use all 800mA - doesn't that run the risk of damaging the device if you go over?

[Paul Newton]

Hi Gorf, What I was trying to say is that the rating of the power supply should be more than the maximum current that will be drawn. This should ensure it runs within its limits and does not get hot or generate electrical noise. If there is a possibility that too much will be drawn through the Netduino's regulators (>800mA), then a suitable system (possibly a fuse / maybe an overcurrent reset circuit) should be employed to stop this happening. Yes, if you used a lower rated power supply, it might help limit the current into the Netduino. But, this would not guarantee that no damage is done to either PSU or Netduino. A side point is that not all the current used will be via the Netduino. Hopefully some will be taken directly to devices like motors and relays. Hence the total needed can be more than he Netduin's safe limit. Have Fun and keep thinking about what forum posters say. Its good to question the advice! Paul

[nakchak]

Hi Gorf Basically the PSU you use for a netduino should be overrated in terms of current to ensure that you have enough head room for the maximum current draw, as running a psu that is rated at 800mA would be effectively redlining the PSU i.e. it would be working at its limit, which often means that stabilisation starts to suffer, MTBF (Mean Time Between Failure) decreases i.e. statistically it will fail sooner etc. As for the maximum current draw for perhiperals you need to ensure that the shield(s) combined current draw doesn't exceed 800mA and if it does provide an additional PSU for that shield/device the only things i can think of off the top of my head that would necessitate a dedicated peripheral PSU would be a motor controller, or a high gain radio transceiver. I haven't looked to closely at the ND PSU/Regulation circuitry but it probably has some current limiting, if in doubt get a multimeter and measure current. If you do need an additional supply you can get a overrated PSU i.e. 5V 2A and a "Y" splitter lead to power both ND and Shield... Nak.

[Gorf]

Thanks for the explanations. The current draw will be even more of an issue now that the idea of daisychaining modules is out.