Ceramic Resonators

[Sling]

Hi I'm trying to build a remote control buggy circuit however getting snagged on the encoder/ decoder. The only ones I could find have a 4-bit signal whereas the schematic I'm using uses a 5-bit signal, and has a 3-pin ceramic resonator connected to the S03 and S04 lines.

As the reader may have guessed by now I'm pretty new to electronics and would like to know exactly what a ceramic resonator does. From the research I've done it either has something to do with filtering or for clock generation...?

Ultimately what I really need to know is can I replace the 3-pin ceramic resonator with a 2-pin one. I'd like to understand why/ why not though of course.

 

[Speakerguy]

A ceramic resonator is a device that resonates at a certain frequency made of a piezoelectric ceramic, and they are generally poor tolerance devices (frequency is not very accurate compared to quartz crystals). They usually have three leads, and have two capacitors built into the device along with the ceramic resonator itself. They are used for clock generation in applications where clock frequency isn't critical (0.5% tolerance is typical).

You can replace a 3-pin type with a 2-pin type so long as you include two external capacitors tied to ground on each pin of the 2-pin oscillator. The reason why is the two-pin devices are just the ceramic resonator without the capacitors included. The caps you need to add to a two-pin resonator are usually very small value (22pF) and the data sheet for the 2-pin resonator will tell you what value to use and the circuit diagram you need.

 

[Sling]

Thanks for the explanation !

One thing though ... the original schematic for my project leads two lines into the 3-pin ceramic resonator. Due to limitations with my encoder/ decoder setup I can only lead one line into it though.

What effect will replacing a 3-pin with a 2-pin resonator have ? It would then be one line and ground I assume.

I'm guessing it will decrease the frequency of the clock ? If so, how could I compensate ? Or is that completely wrong ?

 

[Nigel Goodwin]

What effect will replacing a 3-pin with a 2-pin resonator have ? It would then be one line and ground I assume.

No, input and output, plus you have to add the two capacitors to ground - making it a three pin. One pin and ground wouldn't oscillate.

 

[Sling]

Sorry I don't understand. My original schematic has two lines from the decoder (SO3 and SO4) to the two outer pins of the 3-pin ceramic resonator, and the ground pin connected to ground. These both seem to be input lines.

 

[Nigel Goodwin]

Sorry I don't understand. My original schematic has two lines from the decoder (SO3 and SO4) to the two outer pins of the 3-pin ceramic resonator, and the ground pin connected to ground. These both seem to be input lines.

Presumably they are the oscillator pins?, one is an output, the other on input.

 

[MikeMl]

In the typical CMOS two-pin inverter oscillator, the frequency determining element can either be a three pin ceramic resonator, with the middle pin grounded. You can replace the ceramic resonator with a two pin crystal wired to the inverter pins, and two capacitors, one end of each which is grounded. The three parts are functionally equivalent to what is inside the ceramic resonator, except that the crystal is more stable than the resonator would be...

 

[Sling]

Ok I'm probably being a daftie but I am really struggling to understand this circuit. I've attached a picture of the schematic as I am supposed to build - this picture is using a 5-bit Reynolds Tiny-IR decoder. I cannot find one for sale in the UK so I've using a 4-bit RF600D and RF600E decoder/encoder (from Maplin).

As can be just about seen - apologies for the quality of the pic and the amateurish presentation - the two D3 and D4 lines from the decoder connect to the two outer pins of the ceramic resonator.

So what on earth is this supposed to accomplish when the ceramic resonator isn't connected to anything else?

(I've checked ahead and there are no further lines in circuit plan for any more connections to them).

 

[Mr RB]

That's a standard 3pin resonator with the middle pin grounded.

MikeML already explained how you can use your 2pin resonator to do the same job (see post7 above).

 

[Sling]

That's a standard 3pin resonator with the middle pin grounded.

MikeML already explained how you can use your 2pin resonator to do the same job (see post7 above).

Thanks for the input but my question is how can the ceramic resonator do anything useful when it has no output as far as I can see. The two lines connecting to it are both outputs from the decoder. The ceramic resonator doesn't do anything useful if it has no output.

 

[Nigel Goodwin]

Thanks for the input but my question is how can the ceramic resonator do anything useful when it has no output as far as I can see. The two lines connecting to it are both outputs from the decoder. The ceramic resonator doesn't do anything useful if it has no output.

You seem to to ignoring most of the replies?, I've already explained to you that it's connected to an INPUT and an OUTPUT, with the centre pin to ground.

If you have incorrectly conected it to two outputs, then it won't work.

 

[Sling]

Not ignoring, just don't understand. To be perfectly honest, it seems that I am the one being ignored so far lol.

This is the datasheet for the 5-bit decoder :

TINY-IR-II infrared decoder/encoder ICs

Pins 2 and 3 are supposed to be connected to the outer pins of the ceramic resonator. These are both outputs from the decoder.

I am obviously missing something huge here, please forgive me for that, but I'd really like to understand the circuit.

 

[MikeMl]

I dont see a ceramic resonater mentioned anywhere on the cited page????

 

[blueroomelectronics]

Both the encoder & decoder in those links use the internal PIC oscillator.

 

[Sling]

I dont see a ceramic resonater mentioned anywhere on the cited page????

The ceramic resonator has been encircled in blue.

Please also kindly note that the datasheet is for both the encoder and the decoder. The decoder is further down the page.

 

[Sling]

Both the encoder & decoder in those links use the internal PIC oscillator.

Do you mean by that that the ceramic resonator is superfluous ? In that case, why has it been included in the schematic ?

 

[blueroomelectronics]

Why are you using a resonator? Why not use the PICs internal 4MHz oscillator?

 

[Sling]

This is a project from Electronic Projects For Dummies (I am trying to start simple ).

It is the 'Controlling a Go-Kart, Infrared Style' project in Chapter 11.

 

[Sling]

Why are you using a resonator? Why not use the PICs internal 4MHz oscillator?

There is no PIC included in the schematic - there is a decoder, a hex inverter and an H-bridge.

 

[blueroomelectronics]

Ok so why post the TINY-IR-II design?
What's the resonators speed?
Which PIC are you using?
Which IR detector are you using?

edit:
No PIC? Post a schematic of the complete design.