CJ1M High Speed Counter

[soundwave 0]

Hello All, I am writing to ask the voltage input specifications of a high speed counter on the omron CJ1M CPU23. I had looked at the manual provided and it mentions a 24v for the inputs (but i believe this may be for general purpose inputs). If you could direct me to the specification (I have alot of documentation) Basically i have an ENGINE MPU >>>>> SIGNAL CONDITIONER >>>>>> CJ1M CPU23 The signal conditioner oututs 2.5vpp 5kHz square wave. The CJ1MCPU23 operates correctly with a program i have. I want to keep within specs of the OMRON as this is a design job. Therefore i need to know that this input voltage is ok, OR will i have to aplify the output of the signal conditioner.

[Jay Anthony 118]

Do you mean it works?? Are these open collector outputs? Tell us how you have it wired.

[soundwave 0]

Thanks for the response jay, I have a signal generator running at 1kHz the LPc is online with CX programmer and displays 1kHz. Although I think i have the wiring correct as follows I am unsure if I am on the boundary of the specifications. _______________________ | | | signal conditioner | |_______________________| in gnd gnd out 24v | | | | | | | | | | --MPU-- 29 27 25 CPU23 so basically from the signal conditioner there are three wires +24v LD+ (??Line driver?) 0V the signal to the CPU23, input 8 ( IN8 ), is a 2.5Vpp square wave. The PLC senses this correctly and displays the correct frequency. Do you know what is the threshold ie .7Vpp that would stop the CPU23 from correctly reading the signal. Is this specified in a document? ie W395-E1-03

[soundwave 0]

That wiring diagram did not come out as expected i think the spaces were removed _______________ Signal _________|_IN--------------|MPU conditioner______|_GND-----------|MPU _______________| _______________|_GND-----------|29 _______________|_OUT-----------|27 _______________|_24v-----------|25 so the signal out from the SIGNAL CONDITIONER may need to be aplified to keep within specs

[Jay Anthony 118]

I am surprised that it is reading at all. This is definitely a 24VDC input.

[soundwave 0]

Thanks again Jay, i was wondering where it said it was a 24v input? I have looked at the output on an oscilliscope and see 2.5vpp better yet i hasd added a voltage divider and had .7vpp CJ1M CPU23 high speed counter input was tracking this signal and displaying the correct frequency. I had also changed the range 500Hz --- > 10kHz and still the high speed counter was operating correctly.

[soundwave 0]

Thaks Jay, I will take your advice and look into using a signal conditioner with a 24Vpp signal But note that this is a 24Vpp square wave and not 24VDC but this was just a typo yeah? On the poor attempt of a wiring diagram i detailed a 24V rail, a ground rail, and a 0 - 2.5Vpp signal into the high speed counter input. Is the operation of the line driver LD input (high speed counter input on the CJ1M CPU23) different from using the CJ1M CPU23 input as a regular digital signal? Therefore operation of a line driver input is specified at 5v ? Sorry for any confusion Jay, the specified voltage seemed simple to me but i am unable to find the answer. I have attached the manual page which i was looking at for this. Pages_from_W395_E1_03.pdf

[Jay Anthony 118]

Apparently you are using the Line Driver Inputs on the CJ1M input connector. These inputs meet the specifications of the commonly used RS422 Am26LS31 chip from Texas Instruments. Here is the data sheet for the Am26LS31 chip: Am26LS31_Data_Sheet.pdf

[soundwave 0]

Thanks again Jay that was the exactly what i was looking for but it looks like my 2.5v pp would be marginal even in this situation. I have talked to a local circuit designer and he is going to tweak the old signal conditioner model to output a 24v pp signal for reliable operation. On the personal side thanks for all your help Jay, i am a new to PLCs and therefore the OMRON. We build generators in australia and we will be using the PLC to watch a few analogue variables and digital control. I am sure you will see more of my posts in the future. ( particularly a SCU41 used for a MODBUS master and a slave, but i will save that for another post after i have read other postings on the topic!!!)

[Jay Anthony 118]

Whoa! If you use the line driver inputs do not exceed +5VDC. These line driver inputs are not the same as the 24VDC inputs. Please confirm the numbers of the terminals that you intend to connect.

[soundwave 0]

Thanks again for sharing you knowledge Jay, and opening my eyes to what looks correct but spells trouble. I guess i better explain the application. I will describe the uneducated approach in two parts Design and wiring. DESIGN I am using the High speed counter 0 on the CJ1m CPU23 to display engine RPM. This is achieved by using a magnetic pick up MPU on the engine flywheel a signal conditioner and the PLC. The signal conditioner transforms the sine wave from the MPU in to a square wave out. the square wave is more of a wide pulse output. note that no direction is necessary The high speed counter will read these pulses and i am using the command PRV(881) __________________PRV(881) ___________________ Port Specifier ________0010 ____High Speed Counter Control Data Word____0003 ____Standard Operation then store data, then manipulate data (counter x 60s) / flywheel teeth for RPM... WIRING I have attached an extract from a wiring pdf for a level playing ground. Am i right in saying I will NOT connect it as a line driver I will connect it as a High Speed Counter Specifically i will connect it as "High-speed Counters Using Increment Pulse Inputs" This means 24v MPU signal conditioner signal will be connected to pin 25 of my terminal block and 0v to pin 29. MPU out --------------- Pin 25 Gnd -------------------- Pin 29 The reset is on input 3. I would not be required to reset this input because i am chasing RPM not position control. Right ? Therefore i would not be required to wire input 3? Open Circuit ---------- Pin 8 Open Circuit ---------- Pin 12 Confused? i tend to do that to myself an others, Pages_from_W395_E1_03.pdf

[Jay Anthony 118]

Sounds much better! Did you look at PRV2(883) instruction? It automatically returns RPMs.

[soundwave 0]

Yes i saw that command and said perfect... but compiling brought an error similar to "this PLC version does not support this command", i believe i have an older revision? if the following means anything to you. Revision F PCB Revision BBB Lot Number 020920 Anyhow it is simple matter of converting the frequency to a RPM so thats fine. Now I will venture into modbus territory which should reveal my incompetence, thanks again jay

[Jay Anthony 118]

Sorry about that. Has to be Version 2 or better.

[soundwave 0]

Hello Again, I have just received a Magnetic Pickup Unit (MPU) interface that will connect between my CJ1M CPU23 PLC and a generator. ----------------------------------------------- To clarify what had occurred in this post a summary is as follows. I had connected the MPU interface to a CJ1M CPU23. Not only had i wired this incorrectly but i also had a MPU interface that could not be used for the intended application, thanks Jay. Basically the input to the MPU interface is an MPU. The MPU itself outputs a complete sinewave cycle every time an engine flywheel tooth passes it. This sinewave is transmitted to a device I will call the MPU interface. The MPU interface takes this sinewave as input and outputs a square wave for the PLC. The PLC will count the frequency of the squarewave using PRV(881) and i can determine engine speed. ----------------------------------------------------------- So after sending a few data sheets to an electronics guru he has supplied me with a custom MPU interface. He said he used the line driver chip for cost and simplicity. I had previously expected a 24v dc peak to peak square wave. The electronics guy supplied a much cheaper line driver circuit. I plan to use the line driver inputs on the CJ1M CPU23. I will connect the ground to pin 29 (LD-) and the squarewave signal to pin 27(LD+). I will leave pin 25 unconnected. Now if I use the command PRV(881) I can see the frequency on high speed counter 1 without a problem. NOW THE QUESTION.............................. Looking at the attached PDF I see that the only wiring including the Line Driver is on page 7 of 31. This shows connections to IN9 and IN3 of the CJ1M CPU23. Should I leave these inputs unused? Could I still use the PRV(881) command and count frequency? Thanks in advance. OMRON_CJ1M_CPU23_Wiring_Chapter.pdf