Arduino mega 2560 crystal oscillator

Hello

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

Regards

Pet peeve

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

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.

The crystal has the following marking: SPK16.000G

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

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

What voltage?

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

A brain-dead decision.

How can I solve this problem.

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

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

Very easy to do.

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.

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.

shiu748:
Using a external clock would increase the cost and power consumption of the sensor nodes.

Unit Cost US$3.76
Current - Supply (Max) 6mA

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

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.

But for low cost of US$0.63 Crystal can have lower frequency Stability of ±9ppm only and most have ±30ppm.

Crystals are actually more expensive than comparable oscillators.

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.

50 cents, you're overpaying.

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

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.

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
16MHz Crystal HC49US - dipmicro electronics
28 cents
22pF/50V Radial Ceramic Disc Capacitor - dipmicro electronics
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:

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

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

Lefty

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?

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.

Give an example. You could calibrate out the +- 30ppm frequency deviation in software but how would you propose dealing with the +- 50ppm stability with temperature?

PapaG:

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.

Give an example. You could calibrate out the +- 30ppm frequency deviation in software but how would you propose dealing with the +- 50ppm stability with temperature?

In ham radio equipment they often use a small adjustable variable trimmer cap in place of one of the fixed padding caps to fine tune the resonance frequency of the crystal +/- a few KHz, but that wouldn't have any improvement for the tempo stability variation of the crystal, that you live with or control the environmental temperature of the crystal.

Lefty

retrolefty:

PapaG:

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.

Give an example. You could calibrate out the +- 30ppm frequency deviation in software but how would you propose dealing with the +- 50ppm stability with temperature?

Yeah, I'm familiar with those kinds of hardware solutions but I was wondering how CrossRoads proposed doing it in software.
In ham radio equipment they often use a small adjustable variable trimmer cap in place of one of the fixed padding caps to fine tune the resonance frequency of the crystal +/- a few KHz, but that wouldn't have any improvement for the tempo stability variation of the crystal, that you live with or control the environmental temperature of the crystal.

Lefty