Dear colleauges, I use the Mini 6410 equipment. I want to connect the external voltage input signal from induktiv sensor to the one of GPIO input - EINT. The signal which I get from induktiv sensor is 24 VDC. Would be someone so kind and advice me how to connect this 24 VDC signal to the EINT input? It is allowed or is this signal too high? What is the maximum voltage for inputs? Thank you for your proposals. Evgen
3V3 Using a resistor divider to get 3V3 with 24V on it. How much current can the sensor deliver? I would also include something like a Bourns CD143A-SR3.3 Steering/TVS diode array to protect your IO ports.
A simple and safe input circuit would be to use an opto-isolator with NPN transistor output. Then you just need a current limiting resistor in series with the LED and the transistor can connect directly to the gpio. (collector to gpio, emitter to 0V). Rob
A 2.4K - 4.7K resistor would be suitable for 24V.
Maybe post a link to your opto-isolator solution. > How much current can the sensor deliver? You have to answer my questions before I can suggest something more appropriate. However, for example . . . Resistor divider: 9K in series with a 1K to ground will give you 2.4Volts on the centre-tap. so, maybe an 8K2 in series and a 1K to ground would be pretty close. The maths is quite straight forward, Ohms Law.
http://www.w9xt.com/page_microdesign_pt11_opto_inputs.html http://www.ecelab.com/opto-level-shift.htm http://www.ustudy.in/node/7519 For 24V use a 2.4K - 4.7K resistor in series with LED. Pull-up to 3.3V on GPIO input is not needed if you enable the pull-up on the GPIO input, but adding it wouldn't hurt (10K would be suitable). Rob
Those are much safer solutions. We use Bourns CD143A-SR3.3 Steering/TVS diode array in commercial product.
See http://ics.nxp.com/support/documents/interface/pdf/an97055.pdf as @davef suggests TVS are always a good idea; If you are using multiple gpio in one direction only, you could stick a 74LS245 in front of the cpu; This would give you 5v tolerant 3.3v i/o Then depending on your app use opto + fet/bjt or just fet/bjt;
Sorry for the multiple posts but did not read the op properly. If the input signal is being used only to generate an interrupt then probably the simplest solution is to use a comparator.