Arduino Based Weather Station

[Gina]

Yet another re-design of the ASC is looking promising.  I think I can avoid the need for lens alignment adjustment and reduce both the complication and size

[tekkydave]

I'm not sure if this is relavant to your dodgy nanos but I read the following in the official D-Bot build guide:

"If  you  cannot  connect  or  if  you  receive  a  timeout  error,  you  may  need  to  download  and install  the  CH341SER  driver.  Some  Chinese  knockoff  Arduino  boards  use  a  serial  chip which  is  not the  same  as  normal  Arduino  boards"

 

[sloz1664]

17 hours ago, tekkydave said:

I'm not sure if this is relavant to your dodgy nanos but I read the following in the official D-Bot build guide:

"If  you  cannot  connect  or  if  you  receive  a  timeout  error,  you  may  need  to  download  and install  the  CH341SER  driver.  Some  Chinese  knockoff  Arduino  boards  use  a  serial  chip which  is  not the  same  as  normal  Arduino  boards"

 

Oh.. I've had everything happen to my "chinese cloned. "smoked and died" I panicked into thinking I'd messed up my circuits  Not worked at all and a couple that have died after a few days. Luckily they are cheap and I now have a stock of spares

Steve

[Gina]

I'm currently stuck on the ASC as I have no more Pies to blow up!!  I have a 5m USB cable so I could set up the weather station wind instruments on the side of the ASC and hang it from the guttering to test.  Of course, the ASC will be minus its RPi but with the full casing etc.  Not tonight though as it's raining and the ASC is not fully weatherproof yet.

Edited December 28, 2017 by Gina

[Gina]

The packet of 16 Arduino devices including rain detector has arrived in the post.  As I thought, from China.  So I shall be investigating usage

[Gina]

I though I had details of what all these devices were in this thread but I can't find it

[Gina]

Sometime I need to think about how I shall connect the Arduino Nano that is reading the wind speed and direction to the Arduino Uno in the scope room of the observatory.  I was going to connect it to the Raspberry Pi that runs the ASC but I'm not so sure now.  I've found that the RPi can't run TeamViewer so the file transfer system I had in mind isn't feasible.  There may be something to be said for keeping the systems separate from a fault-finding point of view too.  This doesn't stop me adding a rain sensor to the ASC to tell it to close the lens cover via INDI and this could be combined with either a warning system or roof automation for the observatory for normal astro imaging.  I could add a separate rain sensor to the weather station.

[Gina]

Using I2C between Arduinos is one solution.

[JamesF]

There are also wifi and wired ethernet interfaces for the Arduino, so transferring data that way may be possible?  No idea how much network-level programming is required though.

James

[Gina]

I have an Ethernet shield for an Arduino Uno but it can't go on the present Uno as it already has the data logger shield on it and neither are "pass-through".  But I could add another Uno to the I2C network and plug the Ethernet shield into that.  Or maybe connect the Uno to an RPi if I work out how that might work   I have a CAT6 cable into the observatory.  Guess I could put my gigabit switch in the observatory as I don't think I need it indoors.

[Gina]

I think my ASC project is doomed

[angryowl]

I had a similar problem with my strip board when testing it. I destroyed a DHT22 sensor in the process and had numerous issues with connections, solder points and things just not working as they should. Ended up spending a lot of time going each and every connection and component then testing things separately. At one point I was considering re soldering everything on a proper printed PCB board but I'm now glad I persevered and it paid off!

[Gina]

Please see my ASC Blog for all my test results.  I'm stumped!

[angryowl]

42 minutes ago, Gina said:

Please see my ASC Blog for all my test results.  I'm stumped!

Went through the blog and if I understand correctly you have the buck converter run off 13.8V then the 5V output of that goes into the HAT which then powers up the RPi as well. I'm not very familiar with RPi HAT modules, but could you not just split the output from the buck converter with one going to the HAT and another to the RPi? Would that not circumvent the HAT from the RPis point of view? Of course you'd have to find a way of stopping the HAT from transmitting power to the RPi...

Edited December 30, 2017 by angryowl

[Gina]

That is what I'm doing and keeping the power and grounds separate with the grounds only commoned at the buck converter.  All the HAT does is provide an easy way of connecting to the GPIO pins and also providing a strip board for mounting components.

This is the dew heater circuit, except that I'm using a different GPIO pin.  As can be seen the only connection from the +12v (+13.8v in practice) to the RPi is through the transistor.  The 0v shown is the power Gnd at the input to the buck converter.  The leakage current I measured as around 4 micro-amps.  This has always worked fine in the past.  The stepper driver modules also have separate power and data grounds and the motor output and power side is isolated from the data input and power.  I guess I could use opto-isolators to avoid all possibility (almost) of power and data circuits interacting in a way they shouldn't.  The camera cooling circuit is similar to the dew heater but with the power taken from the +5v side of the buck converter and the heater being the Peltier TEC cooler.  ATM the +5v has not been connected to the HAT.

Edited December 30, 2017 by Gina

[Gina]

One problem with opto-isolators is the input current required.  As I recall the total current available to GPIO pins is 50mA - maybe 10mA to each opto-isolator would be alright.

[angryowl]

So you have separate voltage inputs for the HAT and RPi, and the HAT does not then output voltage via any of its pins to drive the RPi directly. Trying to understand how the HAT works and that you're not powering the RPi through two sources. 

Regarding the dew heater circuit, mine is a bit different/simpler as I can run the N03G N-Channel Mosfet straight off an Arduino digital pin outputting 5V, thus only needing one 10K resistor on the gate. I've the same circuits for the two fans just with the addition of a diode in parallel across the fan inputs. Looks to me like your dew heater circuit shouldn't be the problem?

[Gina]

The RPi uses 3.3v logic or a bit less which is not quite enough to drive even a data level MOSFET as they need 4v.  I've driven those from an Arduino like you as these are capable of +5v output with pull-up.  The +3.3v could be raised to +5v with a transistor and that could then drive an N-channel MOSFET.  OTOH I'm sure there isn't anything wrong with my circuit with P-channel MOSFET as it has worked fine for several previous versions of my ASC (except for using a different GPIO pin - could that possibly be the cause, I wonder ).  No, there must be something else wrong with the wiring on my HAT - I just can't find it.

GPIO5/6 have pull-up whereas GPIO12 has pull-down and that could cause the GPIO to hover in between logic states but that would happen without the +13.8v.  All the same, I wonder, it is a difference.  We come back to Sherlock Holme's classic quotation...

[Gina]

I could do this circuit.  The +5v is the GPIO +5v as supplied by the RPi.  Actually, the 10K resistor could be 100K or more as real protection to the RPi

[Gina]

Camera Cooler Control Circuit.

[Gina]

The N-channel MOSFETs I have are IRLZ44N the L indicating logic level gate control.  This is the transfer characteristic from the datasheet.  Seems to me that this MOSFET could be driven directly by 3.3v logic at up to 30A drain current - I'm only using a few amps.

[Gina]

Peltier TEC is 5v 20W ie. 4A and the dew heater is 70ohms so with 13.8v, a mere 0.2A.  I can't see there being any problem.  I've started removing components from the HAT.  The new circuits are very much simpler   One resistor and one MOSFET.

Edited December 30, 2017 by Gina

[angryowl]

So you manged to get the IRLZ44N Mosfets working directly from the 3.3V logic? If so, that's great as less components are always more desirable in a circuit...

As to what the issue might be, still can't really understand why an unmodified HAT that's designed and tested to work with the RPi could burn through two devices as it so clearly did. Plus you checked the HAT for solder whiskers so it's not like it could be down to a short somewhere on the board. Weird...

[Gina]

Absolutely!!  Probably never know the cause as to find it would mean risking yet more RPies and I'm not doing that much as I would like to know the reason!

I'll test the IRLZ44N to make sure it works on a low voltage - that's easy

Edited December 30, 2017 by Gina

[Gina]