I have no clue what I am doing here... Help?

[Maxxheadroom]

I have not had any experience with PLC's other than understanding what their very basic functions are (My understanding before reading a brief ladder logic article outlining boolean logic was they functioned by if this then that) I have recently acquired a Mitsubishi PLC which I have an interesting intended use for. I have built a mini truck (1980 Dodge D50) which has a small block V-8, now this is where my issues begin the added weight of the engine (about 400 pounds) has caused the front end of my truck to sit rather low. My solution is to run an air ride suspension. Since I will be running air bags in the front I might as well do the rear as well. Here is where the PLC comes into play, most air bag setups rely only on air bag PSI to maintain ride height and level. I don't like this answer especially when there are things like PLC's available. Now my thought at this point is to use a potentiometer in a bracket attached to my suspension components and the frame thus the ride height can now be given a value, and that value can be sent to the PLC. At a given value from the potentiometer the PLC can make the necessary changes which in the case of an air ride suspension will be nothing more than opening air valves (simply energizing a 12 volt coil). With that being said this leads me into my first question, the PLC that I have is a Mitsubishi FXon-60MR-ES I cannot find any information on this particular PLC, specifically if it will accept an analog input (potentiometer) if not I think I can probably achieve the same thing using an encoder however it would seem to me an encoder will complicate the setup further. Also having no experience programming a PLC I have no idea how I can tell a PLC at this value from the potentiometer open this valve and at this value open this other valve. I understand the ladder logic in it's most basic form, however when it comes to telling the PLC to function at given values I am a bit confused. So that is pretty much where I am at, I also have another PLC (I think it is an Omar) it was used to control servo motors, I suspect I could make use of that one by using a few diods in line so instead of flipping polarity to change rotation of the servo motor it would just energize different coils. However I think this particular PLC may be using a pulse signal which obviously would not work to open and close valves.

[Veganic]

Assuming this is a serious post as I don't understand most of it: Value from pot. = P. Logic required : P> x open valve P< x close valve If it's that simple look at this : Manufacturer Siemens Manufacturers Part No. 6ED10521MD000BA6 http://uk.rs-online.com/web/search/searchB...t&R=0499845 It has analogue inputs, for the pot. and can be programmed independently of the software. They also come in 12 Volt DC versions. Probably cheaper than an analogue input for Fx. Probably smaller and lighter too.

[Maxxheadroom]

What I am also confused about while reading through the data sheet for this PLC in kind of implied that it has analog inputs but never confirmed it.

[Sergei Troizky]

FX0n has no integrated analog inputs/outputs on the main unit. The FX0n-3A special extension module adds 2 analog inputs and one analog output. The inputs are hardware-configurable for 0-10V voltage or 4-20 mA current. The resolution is only 8 bits, that is all the range is reflected by only 255 increments. P.S All of the above is as far as I remember, find manuals for more details.

[Maxxheadroom]

I may not be reading this correct but it appears that PLC has one analog out, can a digital out be used with an analog input?

[Crossbow]

The Siemens Logo has NO built in analog outputs. If the unit is DC powered, it will have DC inputs, and 2 of those can be configured for analog inputs instead of discrete inputs. But the resolution might be an issue for you. They're not really high resolution signals. Neither would the FX0N-3A be.

[Maxxheadroom]

How is the resolution an issue (This is a genuin question I have no idea what effect the resolution has on operation) so can I energize a 12 volt coil using digital outputs? Can I use the analog inputs to trigger the digital outputs? Sorry about all the questions but I am really pretty clueless.

[Veganic]

The resolution: If you are trying to measure something imagine having a rule with only inch marks. You know something is sort of 6 inches. If you have a rule marked in 1/32 inches you can now say it say 6 -3/32". Switches are on / off, analogue is not so much 0-10V as 0 to 10V in steps ( for example) when converted to a digital signal. The resolution of the LOGO is 0-1000 for 0-10V I think. Energising coil: I can't see a problem.

[Kings and Barnhams Automation]

hello, from what i understand about this post there are a couple of issues. no1. the mitsi plc does not work on 12vdc as the supply voltage no2. the mitsi plc does not have any analogue capabilties in its current state. however, i think you add an analogue extension FX0N 3A to give you 2 analogue inputs. im not sure if you can add multiple 3A cards to give you more analogue inputs though. if that is true, you will not be able to have the 4 potentiometers you will need for 4 airbags. the programming is relatively simple as what you are trying to achieve is simple comparison. the analogue input values are given to you in specific data registers. the output side will be fine as the plc provides relay contacts for you to put what voltages you want to your solenoids. assuming you can get your 4 analogue inputs back and the plc powered some how, the other problem i can see is that the airbag height can only be adjusted using a laptop unless you can put some potentiometers in or do some digital input logic. the job is certainly possible, and would be pretty easy given the right equipment. i would say that this plc is probably not the ideal piece of kit to use though. hope that help, Rob