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Topic: Arduino mega 2560 crystal oscillator (Read 2963 times) previous topic - next topic

shiu748

Hello

Does anyone know what is the tolerance of the crystal oscillator used in Arduino mega 2560.

Regards

retrolefty

Pet peeve

Quote

it shows the
following part, being a resonator and not a crystal,


There are ceramic resonators and there are crystal resonators, both can be called resonators. And in fact a ceramic resonator could be called a crystal resonator as it's ceramic structure is of a crystalline nature. A quartz crystal resonator also has (of course) a crystalline structure, and is what most people mean when they say, in overly shorthand fashion, 'crystal'.

Been working with crystal resonators sense the 60s where we would sometimes grind the blanks in tooth paste to try and raise it's frequency resonance, or draw with pencil lead to try and lower the frequency. Novice ham operators in the 60s were required to be crystal resonator controlled on their 75 watt maximum morse code transmitters, and not until one upgraded their licence were they free to use a VFO and were therefore no longer 'rock bound'.

Lefty

shiu748

Yes, I assume a resonator is used on the one I am using as I have taken one micro controller  as the ref and measured the skew and its gives me ppm error of upto 1000ppm.

I was trying to study the relation between the applied voltage and crystal skew. But it seems the board has resonator which is not very accurate. How can I solve this problem. My aim was to obtain less than 5ppm error with the arduino without using any external clock.

shiu748

The crystal has the following marking: SPK16.000G

shiu748

Found out from Arduino that Ceramic Resonators have been used on Arduino Mega 2560 R3.

dhenry

Quote
I was trying to study the relation between the applied voltage and crystal skew.


What voltage?

Quote
But it seems the board has resonator which is not very accurate.


A brain-dead decision.

Quote
How can I solve this problem.


You can replace it with a crystal oscillator or an external clock.

Quote
My aim was to obtain less than 5ppm error with the arduino


Very easy to do.

Quote
without using any external clock.


That can be challenging. Crystals guarantted to be in that range are expensive and not very common. A far simpler / cheaper solution is to use external clocks. TCXOs for example are that much more expensive than a crystal.

shiu748

I am doing my research under wireless sensor network and as such the cost and power consumption are very important. Therefore the only option could be replacing the resonators with crystal oscillators. Using a external clock would increase the cost and power consumption of the sensor nodes.

BillHo


Using a external clock would increase the cost and power consumption of the sensor nodes.


http://www.digikey.com/product-detail/en/FOX924B-16.000/631-1071-1-ND/1024776
Quote
Unit Cost  US$3.76
Current - Supply (Max)   6mA

Cost was not that high and power consumption is low too.

shiu748

Here we are looking at not only 1 node, but many nodes hence when it comes to the fact of deploying many sensor nodes then the cost seems high.

But nice suggestion, definitely it will solve the problem where only few nodes are required.

BillHo

But for low cost of US$0.63 Crystal can have lower frequency Stability of ±9ppm only and most have ±30ppm.
http://www.digikey.com/product-detail/en/TSX-3225%2016.0000MF09Z-AC3/SER3628CT-ND/1802879

dhenry

Crystals are actually more expensive than comparable oscillators.

pwillard

To me, that's nonsense.

A 16 MHZ MCU compatible crystal is about $0.50 and add a few more cents for the 2 capacitors needed.  (So maybe $1.00 Max) That's still less than $3.50 you would pay for a crystal oscillator package.

CrossRoads

50 cents, you're overpaying.
http://www.digikey.com/product-detail/en/ATS16B/CTX1085-ND/2640031
35 cents, with proper software can see as little as 1 second drift per day.

caps, 18 cents if only buying a couple, I usually get more
http://www.digikey.com/product-detail/en/C317C220J2G5TA/399-4220-ND/817996

71 cents.

But I typically get my parts here
http://www.dipmicro.com/store/index.php?act=viewProd&productCode=XC7-16000
28 cents
http://www.dipmicro.com/store/C1K22-50
9 cents
46 cents total in 1-lot, and I usually get more to have parts to play with.
Designing & building electrical circuits for over 25 years.  Screw Shield for Mega/Due/Uno,  Bobuino with ATMega1284P, & other '328P & '1284P creations & offerings at  my website.

retrolefty


50 cents, you're overpaying.
http://www.digikey.com/product-detail/en/ATS16B/CTX1085-ND/2640031
35 cents, with proper software can see as little as 1 second drift per day.

caps, 18 cents if only buying a couple, I usually get more
http://www.digikey.com/product-detail/en/C317C220J2G5TA/399-4220-ND/817996

71 cents.

But I typically get my parts here
http://www.dipmicro.com/store/index.php?act=viewProd&productCode=XC7-16000
28 cents
http://www.dipmicro.com/store/C1K22-50
9 cents
46 cents total in 1-lot, and I usually get more to have parts to play with.


And of course there are those 10 cent crystals:
http://www.taydaelectronics.com/crystals-resonators-oscilliators/crystals/16-000-mhz-16-mhz-crystal-hc-49-s-low-profile.html

And 1 cent caps (but you must order ten of them minimum, bummer  ;) )

http://www.taydaelectronics.com/capacitors/ceramic-disc-capacitors/10-x-22pf-50v-ceramic-disc-capacitor-pkg-of-10.html

Bought ten of each so should be set for a while now.

Lefty

dhenry

Quote
A 16 MHZ MCU compatible crystal is about $0.50 and add a few more cents for the 2 capacitors needed.


Those are 5ppm crystals?

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