This is the issue:
I use the K8061 with a touch screen as control panel to send a binary code (8 bits with the 8 D.O.) to a plc. This way I can send 256 different commands to the plc.
This works perfect but:
I want to receive also 256 (or less) codes (read ‘8 bits’) through the 8 D.I. back as feedback, error controls, a.s.o…
As the K8061 only accepts LOW digital signals at its D.I. and plc’s only sends HIGH signals, I have a problem. Solving this with 8 contactors as I do it with the D.O. is no option: the plc send the array of codes every 100 ms, thus too fast for contactors.
Anyone knows if there is a way to “convert” the high signals to low, with transistors or whatever? Is there a kit? A circuit example? A possibility that the K8061 is modified in order to accept High signals? Maybe connecting the inputs with ground through a resistor, capacitor, setting them to low continuously and thus detecting a high signal when this comes in? Without breaking the board of course…
There are some alternative ways to modify the K8061 to accept high signal:
Method 1. Remove the resistor array RA2.
Method 2. Disconnect pin #1 of the resistor array RA2 from +5V and connect this pin to the GND of the board. This is better method but you have slightly “break” the board wiring.
Method 3. Add 1k ohm pull-down resistors from the digital inputs to GND.
I’ll try this asap.
BTW, how high is “high”. the plc gives 24 VDC pulses?
The 24V is just within the limits (30V max) of the ULN2803A specifications:
chipcatalog.com/ST/ULN2803A.htm
Anyhow, I recommend to add series resistors of 2k2 if you use method 3 (4k7 if method 1 or 2) between the PLC output and digital inputs of the K8061.
Thanks
I got an email from one of your co-workers:
“in order to set a digital I/0 with a positive (e.g. 24VDC) signal, you can simply connect a transistor between K8061 input and K8061 ground (collector to input, emitter to ground). Put a 10K resistor in series with the base of the transistor. For the transistor, a simple BC547 will do the job.”
It seems to me there is a big difference between the removing of the array or connecting a pin to +5V, and connecting 8 transistors between the inputs ans ground.
Which one is best now? I’m currently building my 5th 8061, and I don’t want mistakes.
Btw: power in our main rack is 24VDC. I suppose this is ok for the 8061, since a 7805 drops the tension to 5 V and a 7805 can take up to 30 VDC?
thanks for your answer. It’s rather important because I’m installing this in Ukrain, I can monitor it from Belgium, but not repare it from here!
Johan
Do not connect 24V to the K8061. This voltage is too high for the operational amplifiers IC8…IC11. The maximum supply voltage for these operational amplifiers (TLV274) is 16V.
About the alternative solutions to get the digital input accept positive voltage:
The external transistor solution is good. You do not need to “break” the K8061 card as you have to do if you disconnect pin #1 of the resistor array RA2 from +5V and connect this pin to the GND of the board.
You have to cut one trace on the board and add a piece of wire to connect pin #1 of the resistor array to GND.
I think this kind of modification will void the warranty of the card.
Anyhow, the choice is yours.
thank you for your swift follow-up!
I built a few boards now, and they all work: connected pin 1 of the array to ground, after removing carefully the printed connection to 5V of course. Drilled 16 holes of 0.8 mm , cut the printed wires for each DI in order to be able to mount the resistors, placed the 8 resistors 4K7 in vertical mode. It’s nice and it all fits.
Tested: Perfect! THANK YOU.
Why not provide these board with this possibility? A small adaptation with a bridge and optional resistors could make a lot of difference, if you want to use it like I do. Am I the only one?
I’ll stay with the 12V power supply, that is not really an issue. Thanks for the advice.
Would you like to see the application? It is not really what this board is made for, because it is an industrial application, not home or office. But still, a very good alternative if you want to control e.g. 1 plc with 64 DO/DO with infinite possibilities …
Johan
Nice to see that the modification is successfully completed, tested and seems to work.
Thank you for your suggestion about adding the possibility to change the input polarity with one additional jumper. (The series resistors are not needed if the input voltage is below 12V.) Maybe this option will be added to the future products…
Indeed, I’m interested to see your application. It’s always nice to see what all can be done with this K8061 card…
Hello,
it has been 10 years since our last communication, and everything is running all right all the time, in an industrial environment.
I have a new question for a new project in which I will use these same boards (never change a winning team)
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I would like to power it through kit K1823 where I will have an input tension of 24 VDC, converting it to 12VDC, there still is no other way?
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The analogue signals coming in are 4-20 mA, while these K8061 has tension inputs. Normally a resistor of 500 Ohm on the current output of the sensor, should give me a tension between 0 and 10V, which I can calibrate, right?
I still don’t understand what the PWM output is for, wher can I find the right doc?
URGENT, because leaving for Algeria this time…
Had to change my name to jeedee24 as I forgot my password and mail adress changed.
Thanks for your swift response
This should be OK method to convert 24V to 12V supply for the K8061.
This should be OK to get proper input voltage (10V max) for the K8061.
Hi,
Just a small question. In my vba projects, and this has been Always the case:
Connecting a card or cards works fine, but when disconnecting i ALWAYS have to reset the computer.
When I run your demo’s, it can connect without a problem.
I use the 2011 version, which runs best.
Is there a workaround? Resetting something? A call to reset the connection?
Thanks
There in the DLL is only function CloseDevices to close the link between K8061 devices and application.
No other reset functions.
To verify, I installed the 2011 version driver and DLL on Windows 10 (64 bit).
Works fine with the Excel demo VBA K8061DemoExcel.xls.
I can disconnect the card and reconnect it any times without any problems.
Unfortunately I can’t reproduce the issue.
It is an issue with computers which have several versions of office installed. I reinstalled one with only win8 pro and office 2007 (of which I have still so many licenses since we changed to office 365…) and the problem is gone. Stick to front end software of the time the card was developed, and no problem.
OK - I’m glad to hear that you resolved the issue!