I want to use the digital signal generated by the K8059. However I do not need/want the signal to be transmitted by the integrated SAW resonator.
For I want my new circuit to be as smal as possible, my question is which of the components can be spared in that case.
(schematic diagram can be found at esr.co.uk/manuals/k8059.pdf on page 10)
I am extracting the signal directly at pin 3 of IC1. Does that mean I can spare all the components in the left branch? That would be R1, R2, R4, R5, C1, C2, C3, C4, T1, X1, L and LD1 (I do not need the blinking LED). And can I also leave out R3, C6, ZD1 and SW3 if I do not need to change the 32-bit code?
Or would any of those changes cause damage to the IC???
Thank you very much for the answer!
But if I remove everything left of the SW1 and also remove (or do not push) SW3, of what use are R3, C6 and ZD1? As I see it, everything on pin 4 is also redundant in this case.
Please correct me if I am wrong!
Anyway, in the meantime I tried to remove every component but R6, C5, D1, D2, SW1, SW2 and the IC from the circuit and tested that setup. Everything was working fine until after a few days of working on the rest of my project, the IC stopped working properly. If I now press and hold SW1 or SW2, the IC sends out sone sequence of bits (not those two it is supposed to send, but something else) 3 times and then stops until I press again.
I figured the IC might be broken and already ordered a new Kit.
But it would be great to know, what precautions I have to take, so that the IC will not get damaged again!
You have accidentaly put the unit in a mode where it only puts out a single burst instead of a continous stream of data.
You can return it to normal operation by pressing and holding the left button. Now press the right button 3 times. You will have to do this within a second or it will not work and you will have to restart.
Do NOT remove R3, C6 and ZD1.
The masterclear (pin 4) is not equipped with an internal pull-up, so an external one must always be supplied.
As for C6 and ZD1, they limit the voltage to less than 5V. If you remove them, you will destroy the IC.
Ok, sorry if I am still missing the point you are making, but if I remove all the components left of SW1 (excluding the battery), my schematic looks like this:
As I see it, there will be no current through R3 unless I connect “???” with something.
So just to be shure: To use R3 as a pull-up, I would have to connect “???” with +12V of the battery, or what do you mean by that?
Sorry for your troubles and thank you for your patient support!
Mark
EDIT: Resetting the IC and resetting the reciever fixed the problem with the transmissions. Thanks for that!
That just leaves the question about a “save” modification of the circuit.
Do NOT connect R3 with the +12V, since the PIC is a 5V device.
Leave it connected to pin 1 and pin 4 of the PIC.
??? is +/- at ground level when any of the buttons is pushed.
Please note that this circuit has been designed to be used ‘floating’, i.e. without anything else connected to it.
We understand that you will connect some external circuitry to the ‘OUT’ line.
This will probably work fine, but please not that it is possible the ‘OUT’ pin floats to +12V when none of the buttons are pressed.
Make sure your external cicuit can handle +12V at its input.
Ok, now I am finaly on the same page!
Your advice to leave R3 connected to pin 1 and pin 4 of the PIC confused me at first, because there is no connection between R3 and pin 4 in the schematic. But after checking the actual layout on the board, I realized there are dots missing in the diagram to indicate the particular wires are actually connected to each other: One between pin1 and R6 and another one under pin 8.
So the modified schematic looks like this:
And now I see the use of R3, C6 and ZD1.
Anyway you may consider completing the schematic to avoid further misunderstandings…
Also thank you for pointing out the danger of the floating output pin! I did measure this effect and took precautions already.
EDIT:
If I could supply 5V out of my other circuit, could I connect those directly to pin 1 of the PIC?
If you supply 5V direct to the IC, then you can omit ZD1 & R6 and you can get rid of the Schottky diodes D1 and D2.
Connect Vss of IC and switches direct to GND. C5 can also be omitted.
Perfect!
I supplied 5V out of my circuit to the PIC directly, omitting R6, C6, D1 and D2 (kept ZD1 as for now, just to be shure) and everything works fine!
Thank you for the great support!
Mark
EDIT: If I short-out C5 I get a lot of stange noise on the output. So I will probably just leave C5 in the circuit.
