Re: New OCS developments

Howard Dutton

On Fri, Sep 24, 2021 at 01:43 PM, koal01 wrote:
Howard, here are some words around this new OCS design :

Much more capable on the software side with Teensy3.5 and W5500 for Ethernet.
Great ! i built the W500 component with a Teensy 3.2 this year for the Maxpcb in Onstep, it is very compact and works fine, is it the same than the one in onstep ?
Same as OnStep uses.

As for the MCU, the mega 2560 is limited, the Teensy 3.5 or 3.6 will certainly bring a more stable solution, why not an ESP32 wich is cheaper and powerful as well ?
Cheaper yes.  More powerful than a T3.6 is debatable.  The 3.6 is much faster.  The 3.5 is about as fast.  The ESP32 downside is the lack of pins, that can be worked around by imposing limitations and/or using additional h/w but it's a hassle and complexity.

The SD card will now be directly on the MCU and not the ethernet shield, hope you won't have debugging extra job around charts
Shouldn't be an issue.

Switching voltage regulators for both 3.3V and 5V for respectable current supply levels on both of those rails.
Howard i can't see the level shifter is it downside on the pcb ?
There is no I2C level shifter as the MCU is 3.3V already.

This has 10 relays, 4 solid state (1A), 4 mechanical (16A), and 2 other "relays" that are high current n-channel MOSFETs for running large DC motors (like my roof motor.)  All are optically isolated.  It also has a header to allow plugging in a cheap eBay 8 channel relay module for expansion to 18 total relays.
Yes the 2 high current relays that i intend to use for moving my shelter which is on rails and not a roof opening shelter, i'll certainly use Nema 23 or 34 certainlu RE5 and RE6 ones i can see on your design

Provision for an BME280 onboard for inside TPH monitoring.The SPI interface has the correct pin order and orientation so the common eBay DS3234 RTC modules can plug right in.
Good, the Ntp time is not accurate in my current setup but i had to remove the DS3234 i initially installed as it was in conflict with the SD card on the ethernet shield using the same SPI interface
The OCS3 will use OnStep's TLS class (portable code, basically a library) with all that brings (DS3231, DS3234, GPS, and I'll add the NTP to it.)

There are 12 total input channels, 6 digital only and 6 analog.  Most are current limited and ESD protected.
Good, many inputs for future needs
Not mentioned are the 2 TVS diode array SMT components on the PCB back.  Optional, and not too difficult to solder (fairly large for SMT) they save a lot of PCB space.  The ESD protect the 6 digital inputs, 4 analog inputs, and the I2C data and clock lines.  I actually changed the design of inputs a little, there are now 4 digital, 4 analog, and 4 general purpose that can do either analog or digital.  Added a bit more flexibility having the general purpose inputs.

The I2C interfaces use RJ45 connectors so sensors can be plugged in using Cat5 Ethernet cables.  I settled on a scheme where 3.3V (or 5V on I2C 2) and +12V are present too for powering those sensors.
Nice, the RJ connectors are more reliable than Molex for that purpose, what kind of I2c component can work on 12 V ?
Not really for I2C directly but anything else that might be at the end of that cable that might need power and 12V is much better for delivering that than 3.3V or 5V.  Say one wanted to run a little heater on an optical window, etc.  BTW the 3.3V and 5V outputs on the PCB left side and on the RJ45's is polyfused at 500mA.  The 12V uses the main blade fuse.  If you happen to short an I2C 3.3V or 5V it shouldn't bring the OCS down (its onboard 3.3V/5V will still be there.)

And there are two TTL serial interface
Can you give examples of TTL components on that interface ?
Another Arduino.  OnStep.  Etc.  You could also adapt to USB. Or Bluetooth.  Etc.  Usually these run on 5V (with their own regulator to make 3.3V) so 5V is there on the connectors.

Many components can be ordered directly from LCSC which is associated with EasyEDA where this PCB was designed and will be ordered from
Good, when the PCB will be avalaible it would be nice to find easyly the components, some relays where not easy to find in the previous version, not your fault but manufacturers deciding to stop selling relays hard to find.

Other questions and observations :

Thank you for all these changes in this brand new design, very nice job !
The w5500 is a nice improvement and a so good heritage from an Onstep feature
Will there be any weather forecast feature integrated in OCS even through an API with a remote Weather solution ?
Some demands on the previous version like extending periods for charts will be possible in this design ?
I'll consider additional features once OCS3 exists.

Will the commands to query sensors remotely change, i'm python scripting them and it works nice so any changes will havee to be taken into account ?
I plan no changes there.

Join to automatically receive all group messages.