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The week is almost over. Can breathe and go back to my thing.

 

 

so range is going to be really poor on 1Mbps and 2Mbps.

Looks like you're right on that one. I tried 2Mbps, 1Mbps, and 250Kbps. The range seems to be inversely proportional to the rate. So, I programmed both stations to the lowest rate. With one station still outside, I actually moved the base station to my office and I'm still receiving updates.

 

I found the code in the forum for checking the voltage, I believe by reading channel 11 of the ADC, which returns 1/2*(VCC-VSS) Can this be a reliable way for checking batteries health?

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The range seems to be inversely proportional to the rate. 

Yes, this is a physical property we call Eb/N0.  Basically it just means that if you have a longer bit, there is more energy in it, and therefore higher signal-to-noise.

 

The higher baud rates on the NRF24 have some additional attributes that negatively impact SNR beyond the Eb/N0.

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Yes, this is a physical property we call Eb/N0.  Basically it just means that if you have a longer bit, there is more energy in it, and therefore higher signal-to-noise.

 

The higher baud rates on the NRF24 have some additional attributes that negatively impact SNR beyond the Eb/N0.

Awesome info jpnorair - never knew that.  I'm planning on a project using the NRF24 and want a decent amount of range (50ft is ideal).  I tried to use the Anaren BP before and could only  get something like 15ft.  It's nothing that requires a lot of speed - it's a fireworks launcher.  It's just for small stuff, but distance is still important since it's for my kids to light the fireworks.  Hopefully running at  a low speed will  give me all the range I need!

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I found the code in the forum for checking the voltage, I believe by reading channel 11 of the ADC, which returns 1/2*(VCC-VSS) Can this be a reliable way for checking batteries health?

I found my answer. Channel 11 of the ADC can not be used to reliably read the battery voltage. I ran the msp430G2553 chip on a breadboard with 2.2V and it still reports maximum voltage. There must be another way to check battery level and I will find out :-?
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The boards came back. The peoples at Oshpark helped me on this one. They must have changed something(added clearances) because there is no short on the board.

I did make a mistake though. On my design, the radio module(cheap nrf24l01 from ebay) was supposed to be soldered on a dual 4 pins row, instead I used an IC footprint. Now, I must find a way to make it work.

For the first board ever made, I'm happy with the mistake. Can live with it. :smile: Now time to solder an try it out.

 

post-228-0-95991200-1361854638_thumb.jpg

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  • 4 weeks later...

Hi,

 

Finally found the time to populate the board and test it. Everything worked as planned. Programmed it using another LP as seen in the picture.post-228-0-63275500-1364184026_thumb.jpg 

Then added 9v battery and set it up outside.post-228-0-04001500-1364184073_thumb.jpg

Tested current consumption using my "poor quality" multimeter. In active mode, it uses 8.42mA and 3.65 mA in standby. I don' know why this feel like too much current ... Maybe it is.

 

Now working on elaborating the code.

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As Roadrunner eluded to earlier, the 7805 is pretty power hungry.  Quiescent Current (based on the data sheet I grabbed) is about 5mA typical and that doesn't even take into account the losses for the 4V drop across the regulator.  I am guessing that the 7805 might be a significant part of your current consumption.

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you gotta love that feeling of holding the first board you designed in your hand and knowing every nook and bend and whatnot about it, atleast for me :smile:

 

It sure does feel good :)

I calculated that being active 2s and on standby 58sec, my 400mA 9v battery will last approx 4days. Which is very poor. Since both the msp430 and the radio have low power options, what do you recommend I use for power conversion if I want to stay low power?

Looking at the second iteration of the board already. Couple of things that I'd like to integrate:

  • Rx/Tx pins/pads for easy debugging
  • try smaller footprints to further reduce the size of the board.

This would have to wait though. Very busy with school and work for now.

Thanks to everybody for your comments.

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The power in general seems very high.  

  • Your boards should be doing < 5uA in standby -- and 5 uA is generous on the high-side.  
  • In active mode, there is some radio on-time and some MCU set-up time.  The MSP430 probably doesn't need more than 3mA to be active (check the datasheet, I don't use the G-series parts so I can't tell you from memory).  The RF unit probably uses on the order of 20mA for transmit and 15mA for receive.  check the datasheet on that, too.  The average current during active is the weighted average of the time spent in setup and the time spent in RF.  It's something easiest to measure on an oscilloscope.

 

To put things into perspective, on a WSN board I'm testing the standby current is 3.2 uA.  The average active mode current per one duty (about 800 us) is 4.3 mA.  This model is not terribly different from your model, except that there is a subtraction by a constant.  So, it might be just that you are testing during debugging (which adds some extra current), or it might be that you have a low resistance short somewhere, or it might be that you are not putting the RF module to sleep properly.  I would check those things.

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you gotta love that feeling of holding the first board you designed in your hand and knowing every nook and bend and whatnot about it, atleast for me :smile:

Sure, until you realize how many boneheaded mistakes you made on it. Re: my own board ha.

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