And the various provisions on the shield pcb
- Solar charger. Switching power supply which converts charge voltage to 13.8 VDC to charge a sealed lead acid battery. Uses LT6809 2 amp switching regulator.
- Switching power supply providing 5VDC to the shield. Uses LT6809 2 amp regulator. The supply can be shut down by the Electron. A ZMR500 LDO linear regulator is wired in parallel with the LT6809 to supply minimal 5VDC when the switching regulator is turned off. Allows the circuit to run at minimal current.
- High side switch using a VN751 which switches 12VDC to both the SDI-12 and discrete input sensor terminals.
- Analog input amplifier which takes 0 to 1 VDC input and provides 3VDC to the Electron AI or DI inputs.
- Circuitry using a MAX487 to convert Serial 4 to the single wire SDI-12 data line. Alternatively the full RS485 signals from the MAX487 can be routed to the 3 terminal connector.
- Watchdog timer and supervisory reset function provided by an LTC2918 chip. Monitors the 3.3V OUT of the Electron and forces the Electron into reset if this drops below 2.5V.
- Provision of 64K Byte FRAM chip running off the standard Electron TWI port.
- Provision of 500 M Byte flash chip running on the standard Electron SPI port.
- Provision of microSD connector running on the standard Electron SPI port.
Can I order one of these boards from you?
Also, I am curious what the connectors are you are using? Do you have a BOM I could look at, or a part number?
@hwestbrook Heath, I can’t supply any boards at the moment, we are building a few of the new revision up by hand and doing field testing with them. Not sure when we will do a production run, that depends on whether we find errors. But so far it is looking good. I will keep you in the loop.
The 3.81mm connectors (green) are the Digikey part number series ED1949-ND Also Plug ED2456-ND
The white 3 and 5 way communication connectors are the Digikey part number WM18903-ND series
The LiPo battery connector is Digikey part number 277-2337-1-ND
The SMA antenna connector is Digikey 931-1361-ND
I will keep you in the loop, there are a few people interested in it so I will keep updating progress on this thread
The typical packaging we envisage for the finished product. It is getting there and testing and firmware development is proceeding well.
Wondering if you’ve moved ahead on building any of these. Would like to get one to test out.
@hwestbrook I think we can spare one of the units we built up for testing if you are interested. I will have to check. If you have an Electron on hand it would be best if we sell you the board complete apart from the Electron and you can decide if you want to solder it yours on or fit sockets. Let me know. I can’t see us making any hardware changes when we do the production run, it is all working well. I am happy to share the libraries we developed to drive the various sections. Probably at this stage the main program which ties them all together we will keep to ourselves, partly because we have made a big investment in that and also it may not really be what you want to do anyway.
We can sell you the board, complete with front/back panel for $US100 plus freight. I have no idea what the final product will sell for, probably about that figure but we have to get quotes for manufacture yet.
Let me know. Regards
I have a few questions about the library and shield.
- According to the library normally without shield connecting directly from sensor SDI12 cable to port 4 of electron should be able to work?
- Did you have a final production of the shield? I would like to purchase one from you.
What I’m trying to achieve now is to use electron to read data from sensor (SDI-12 communication) and send to my own server to display in web browser online. Do you have any suggestion what should be the step or do you have any guide with this?
Sorry for the stupid question, I’m really very beginner.
@mekunka You can’t connect the SDI-12 sensor directly to the Serial port 4, The SDI-12 sensor has a 5 volt data line which goes in both directions so you need some sort of circuit to combine serial 4 TX and RX into the one line. We use a circuit using a MAX487 chip (normally used for RS485 communication) to combine the signals and send and receive the 5V one.
The library assumes that this interface is used.
We do not have any spare shield boards at the moment, planning a production run later in July at this stage
Thanks for your interest
Thank you for your prompt reply. I’m now thinking about to use arduino uno communicate directly with SDI12 and then write and read from electron to arduino instead, which means I will use arduino uno as a shield but the problem is that, I have to do programming 2 ways but that might be easier for me since I have almost 0 knowledge in hardwares. Please let me know when you have a spare shield left, I would like to purchase one
I will do, there is an arduino library for SDI-12 now, it uses a software serial port and one pin to do the communication, I think you may have to use a 5V Arduino to make sure the signals are at the right level
@pNrie Is it possible to use Max485 module https://www.itead.cc/max485-module.html instead of Max487 chip? According to your diagram, is it possible that B connection can port with SDI-12 and leave A connection empty while RO, RE, DE and DI connect similar with your diagram.
It looks as though you could because you have access to the control pins which you could wire up as per the diagram I posted. I assume the A and B RS485 lines are on the green terminal. You need to bias the A line at about 2.5V to ensure that as the B line moves between 0 and 5 volt that the receive signal RO is correct.
It should work