PLC, STM32 Development

Ethernet/GSM Module

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I can use my Universal Communication Adapter to code most of what is on this card, so I am in no hurry to order this PCB. The fact is I miss package sizes, so I just need to sit & wait a little for now. I am however running out of space in front, so I am considering increasing the size from 65mm to 75 or even larger. I am going to draft some of the other PCB’s to make up my mind.

I dropped sound support on this and I am a bit disappointed with the need for a 4V/2A PSU that require some extra space. This makes the GSM module much larger than you expect it to be. One nice thing about this PSU is however the digital on/off pin enabling me to switch off GSM power completely. I am drafting with SIM800C to get experience, but I have not decided what module to use yet. It is sometimes very difficult to choose without experience so you see what the differences mean.

I selected SIM800C over M590E due to sound support, but as I realize that sound is analogue only I need to look into the other (and maybe far more expensive) modules for digital sound support. The issue here is that using am ADC/DAC is possible, but as the sound is digital inside the GSM module I would rather swap to a module that offer sound IO on digital packets to avoid the extra noise. I need to work on this a little – nothing is settled yet.

I am also considering moving the GSM module to the top to let the antenna be on “top”. to avoid that it is in the way of Ethernet/Wifi.

Also, the difference between this and the All-In-One Home Central is very small at present…

PLC, STM32 Development

PWM Module 21×5-48V/0,5A

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This makes use of the ULN2003 that can take 5-50V input and drive 0,5A. This simple chip allows for multiple PWM channels that can be used for anything from relays to small steppers. This draft suggest 5 stepper motors and a actuator. The connectors on this is a Challenge due to the available width.

Home Automation, PLC, STM32 Development

PWM Module 8×12-48V/3A

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This draft illustrate a PWM module based on the driver of the motor controller we made earlier. We use a concept of a gate driver and 2 x HEXFET to create a Half H-Bridge. We will need 10V+ due to the gate driver, but we only need 1-3A on this one. I think it is realistic to have 8 channels, but if not we will reduce the numbers. PWM out will be anything from constant voltage to 0 duty. We will pulse on/off and use a 2nd frequency to pulse (regulate voltage) within the main pulse.

This targets solenoids with 12-48V and <3A.

PLC

GSM Schematics

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Double click on the picture to see the larger version …

The SIM800C uses a 4V PSU that need to support 2A. All the circuitry on top is PSU related according to reference – I have removed some, but need to see the PCB layout before I consider the rest. Also, I am not sure I bother With the USB Interface. But, well it’s an ealy draft anyway…

I have not Connected the voice on the Ethernet module due to Space concerns.

PLC, STM32 Development

Ethernet Module

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Just an early 3D model of the Ethernet Module including Ethernet, Wifi and GSM based network connections. I have to add the 3D modules of the sim card holder and antenna that also goes to the front, but I am running out of space. These modules are only 80 x 65mm, but that is in my opinion needed for mobile PLC’s.

Plain

Plain – hitting the road

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I wrote lengthy blogs about Plain syntax and concepts earlier this year and want to wrap up the specifications and get going. The challenge with pushing on ideas and concepts is that you start getting blind-folded and stuck as you push for results. This is why I prefer new concepts to mature because what seems like a good idea one day might not the second day. Many of the concepts in Plain have however evolved over several years as I started on this far earlier than this blog.

The difference with other programming concepts is that I don’t want to create another language, I want to evolve the way we work so we can achieve more with less. Plain embrace several new concepts aiming for that, but this is untested theory. I believe it will work as expected, but I am also prepared for setbacks as we move forward.

Plain is also more difficult to achieve than normal programming languages because I need electronic devices supporting it and an established infrastructure to build on. Things take time, but we will get there.

Thanks for reading.

PSU

3.3V 5V, 12V or 15V Switched PSU

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This is the PCB for my switched PSU. It takes 40V in and can be made to produce 3.3V, 5V, 12V, 15V etc. With Pictures you loose a bit feeling of the actual size, so I put a TO247 transistor next to it – this is the smallest PCB I have made so far.

It is designed as a drop in replacement for linear regulators since I often need 2-4 PSU’s on a motor/PWM design. Regulating from 40V to 3.3V means you use a lot of Power. Will assmble a few of this for testing later.

Home Automation, Plain, PLC, STM32 Development

PLC – 24-bit Analogue Input Module

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This analogue input module uses a ADS1256 that allow 8 channel input with 24 bit precision and 30Kbps sampling rate. With a programmable gain amplifier 1:64, programmable filter and support for single or differential inputs as well as calibration this board can cover most ADC needs.

The input here can be 8 stand-alone channels or 4 differential channels. A stand-alone channel will measure voltage between input and ground, while a differential channel measure voltage between two points. The later is more flexible as it also can be used for current loops. The challenge is however that different usage require different line adaption circuitry, meaning we will need different analogue boards.

My primary focus is on typical analogue sensors like light, temperature etc. This example circuitry feed a voltage in that is split over 2 resistors with the sensor being the 2nd, variable resistor that changes with light, temperature etc. A typical ADC line driver is shown below:

This is the water sensor I illustrated earlier where we use a specialised PCB as a resistor. R1 need to scale the input so we get 0-3.3V out to the ADC. The capacitor is only a filter. More important is that we can Interface to this in two ways – we can create a 2 pin connector for the external resistor only, or we can supply +/- and expect an analogue value in. Many modern sensors will require the last 3 wire Interface as they provide their own specialised analogue interface.

The main drawback with this technique is that we can only have a limited distance between sensor and the ADC since the wire will start acting as a resistor that needs to be taken into account. A different analogue technique that can be used over 5km is a current loop – I will consider making a Board for that later. But, also remember that we have RS-X based sensors that can cover some distance in wiring.