getting I/O for 24V device.
OakGraphics
Posts: 202
Howdy gang,
I am trying to talk to a Stepper motor controler that is using industrial voltages. (24V) for it's inputs and outputs.· I know this might be a basic thing but I was wondering what the circuit would be to have a 24VDC input signal turned into something that TTL (+5VDC) could handle, and vice-versa.· I probably should use opto-isolation as well.· Worse - I need to repeat this 16 times. (16 input / 16 output).· I have been looking for a canned solution but to no avail.· Any ideas on simple circuits, or solutions?· I suspect a pull-up resistor would work if I sinked the current for output/input, but what about if I need to inverse the logic for that?
(surely DeSilva could solve this for me in a flash!
)
·
I am trying to talk to a Stepper motor controler that is using industrial voltages. (24V) for it's inputs and outputs.· I know this might be a basic thing but I was wondering what the circuit would be to have a 24VDC input signal turned into something that TTL (+5VDC) could handle, and vice-versa.· I probably should use opto-isolation as well.· Worse - I need to repeat this 16 times. (16 input / 16 output).· I have been looking for a canned solution but to no avail.· Any ideas on simple circuits, or solutions?· I suspect a pull-up resistor would work if I sinked the current for output/input, but what about if I need to inverse the logic for that?
(surely DeSilva could solve this for me in a flash!
)·
Comments
DigiKey carries the Grayhill racks and modules, which are typically less expensive than Opto-22.
-Phil
Post Edited (Phil Pilgrim (PhiPi)) : 10/25/2007 6:13:41 PM GMT
I was looking at these guys·because they have 16 channel of TTL to 24v, and another board that does 24V to ttl, but the total cost comes out to about 500$ for both of those - slightly out of my budget.·· I will have to see what is available in UK / Europe for the Opto-22 and Grayhill stuff.
-Daniel
First, digital logic signals can always be visa-versa altered (0 to 1, 1 to 0) by use of a logic device called (unsurprisingly) an inverter. The general logic device part number for such a device is 74xx04. They come in different withstand voltage ranges (TTL, CMOS, etc.) and in different numbers of inverters per single device (6 and 8 are common). Each inverter section is independent, and operates on its own. It only needs to be placed in-line with the signal to be inverted and there are no "controls" for it.
Opto-couplers (4NXXX devices) can be had with inverted and non-inverted outputs, so they stand on their own in that respect. They also can be had with diffferent output means (open collector, Darlington, etc). Since there are two separate devices inside the IC (photo transistor, photo receptor), it is even possible that they may be availble with differing input and output voltages, although I've never investigated that aspect.
Opto-coupler relays (OPTO22, Grayhill et all) can often be had with various input and output options which may help to reduce any external circuitry you may be planning. Once you have determined which unit is appropriate for your application, by use of the manufacturer's web site, there are even surplus resources for obtaining them at discounted prices. Marlin P. Jones is one such supplier (MPJA.COM).
Lastly, straight forward inversion can be done with a simple transistor circuit as well. All current and voltage ratings, as well as transistor type need to be taken into consideration.
Regards,
Bruce Bates
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