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Angel Valdez

I need help SSI Encoder with Micrologix 1400

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I have a project where I need to use an SSI Absolute Encoder with a Micrologix 1400 PLC. I've never done this and need help. The SSI have a Clock and Data signals that are different from anything I've ever used. 1.Can it be done using the HSC inputs? 2. I found an AMCI card I could use but I am trying to keep everything AB and in the Micro Family. 3. I don't want to use Gray Scale encoders because of the number of Inputs I have to use. Trying to package a small enclosure and don't much room left. 4. AB sells an SSI encoder but they don't have any info on hooking up to anything other than Point IO module.(kills my budget) Thanks and any assistance would be greatly appreciated. ~Angel

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1.Can it be done using the HSC inputs? No. 2. I found an AMCI card I could use but I am trying to keep everything AB and in the Micro Family. Never used it, but it looks good. Go for it. 3. I don't want to use Gray Scale encoders because of the number of Inputs I have to use. Trying to package a small enclosure and don't much room left. You could consider an Ethernet/IP encoder, but the cost is going to be higher most likely. AMCI Encoder Rockwell Encoder 4. AB sells an SSI encoder but they don't have any info on hooking up to anything other than Point IO module.(kills my budget) This is because they don't have any option other than a Point IO module for the Micrologix. There is no native option for SSI on the Micrologix Hope that helps. Best of luck! Edited by MrAutomation
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That AMCI 7160 series module is the best solution for connecting an SSI encoder to a MicroLogix 1400 controller. Applications like yours are the whole reason it was developed, because there is no other effective way to connect an SSI encoder to a MicroLogix 1100 or 1400 controller. I use SSI encoders with Turck network gateways to DeviceNet and EtherNet/IP, as well as with the 1734 SSI input card and the 1756-M02AS. But that's for bigger ControlLogix systems. For the MicroLogix 1400, you're going to have to accept the budget hit and get the AMCI module.
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As I research this more and more trying to will this to work with out that card(I'm stubborn) I found this wiki info on it. http://en.wikipedia.org/wiki/Synchronous_Serial_Interface Looks like the communication of the Data and Clock is done via RS-422/485. Going to lead my self down this path see what happens. Will post results either way. The engineer in me won't let it go even though smarter people are telling me to get the card lol thanks again

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"MicroLogix 1400 controllers support various protocols on the RS-485 network, including DH-485, DF1 Half-Duplex Master/Slave, Modbus RTUMaster/Slave, ASCII and DNP3 Slave protocols."http://literature.rockwellautomation.com/idc/groups/literature/documents/um/1766-um001_-en-p.pdf Page 70 SSI might be loosely based on RS422, but in the end it's a different protocol, right down to the driver level. No matter what type of hacking and reverse engineering you do, you won't be able to take an RS422 port on a PLC and convert it to an SSI port. Maybe you could do it on a PC with software, but you would have to be able to directly manipulate the data on each pin. Besides that, as you'll see in the terminal connections, the RS485 port on the MicroLogix is for 2 wire RS485, and is not compatible with 4 wire RS422. And certainly not with 4 wire SSI. The only possible option I could see is to create your own embedded chip that you designed yourself, modifying the RS422 components to match the SSI requirements. Oh wait, you just created an external SSI module, and AMCI already did that for you! Edited by MrAutomation
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An anecdote: I was researching the National Instruments RIO platform and needed an SSI input. "No problem !", the salesman said, but I couldn't find an SSI interface module in the literature so I pressed him for an example, thinking there must be a limited or unreleased module. He came up with an example where somebody had used their FPGA controller with a discrete I/O card to implement a "bit-banging" SSI port. The FPGA and I/O circuitry on NI modules has virtually no buffering or isolation and it's so blazingly fast they were actually able to write their own firmware to do SSI. This is not possible with the MicroLogix 1400 serial port. It's a UART, a fundamentally different bit of silicon. "All you need to do is write your own firmware on an FPGA" is a wonderful product development challenge but wildly impractical if a couple hundred dollars is the limit on the budget.
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Thanks guys... I'm realizing the same things here. Called into Rockwell and I have them shacking their heads why they don't have something available since they sell the SSI Encoder as well. I'll post any feedback they give me.

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