Robert Brown Arduino dew controller build, step by step

[brown_rb]

Yes I have used the keystone connectors in one of the builds I did. They are fine for the current and take up around the same space as the rj11 socket. I bought them from aliexpress.

[Gina]

Where multi-strand wires are too big for crimp connectors, I too have removed some strands to slim them down but not used solder as that defeats one advantage of crimp connectors - that of not being affect by heating with high currents.

[JamesF]

2 hours ago, wimvb said:

If you only use 1 row of pins, you may be able to use v-board and make your own board mounted sockets. You could then even mount several next to each other on the same board. Just beware, some have pitch .07", others .1"

Nice piece of lateral thinking, Wim :)

I wasn't aware that different pin pitches were common so that's useful to know.  Looks like the sockets I have are 0.07" between the pins.

James

[wimvb]

9 minutes ago, JamesF said:

Nice piece of lateral thinking, Wim

I wasn't aware that different pin pitches were common so that's useful to know.  Looks like the sockets I have are 0.07" between the pins.

James

Neither was I, until I checked it. I was aware of the 0.07"/2 mm version, which I thought was odd since 0.1" is a standard. Then I found some with 0.1"/2.54 mm pitch on line but these are interlaced at 1.27 mm. 

You could try to bend the outer pins a little. Or use the copper side of a v board and surface solder them. 

Edited January 9, 2020 by wimvb

[Dr_Ju_ju]

Another reason for making your own PCB, in that you can use standard connectors e.g. https://uk.farnell.com/amphenol-icc-commercial-products/rje01-660-01/connector-rj11-jack-6p6c-1port/dp/2751501?st=rj11

It doesn't matter then what pitch \ pinout they are, as the layout program will take that into account....

 

[JamesF]

4 hours ago, Dr_Ju_ju said:

Another reason for making your own PCB, in that you can use standard connectors e.g. https://uk.farnell.com/amphenol-icc-commercial-products/rje01-660-01/connector-rj11-jack-6p6c-1port/dp/2751501?st=rj11

Certainly.

However I think there are many people who would be capable of completing this project for whom making a PCB might be a step too far, either because they feel it is beyond them or because it's not a practical solution to just produce one board.

James

[Dr_Ju_ju]

I always do photo resist sheets, so I can make many identical pcb's, & have done....

[JamesF]

I got hold of some GX12 plugs and sockets to get a better feel for the size.  The largest part is the retaining nut for the socket and that is no bigger than the 6P4C socket is tall, though a little wider.  I think with a small adjustment to the spacing of the sockets I can make that work so I think I shall give it a go once I can find a source at an acceptable price for the number I want.  I might just need a couple of turns of insulting tape around the outer sheath of the sensor cable to give the cable clamp enough to grip on.

James

[JamesF]

All the pin headers that I'm going to use are now in and there aren't too many holes left, especially as the two four-pin headers that are left won't be used (the ones for the Bluetooth connection and the HTU21D humidity sensor).

For the pin headers I used much the same method as for the resistors: put a number in place and then gently press a flattened piece of blutak down over the top to keep them all in position whilst the board is flipped over and everything soldered into place.

As I mentioned before, the five diodes have leads that appear to be 1.1mm in diameter and are too big for the holes in the PCB.  In my previous build I soldered the leads to short lengths of wire that would go through the holes and fitted the diodes vertically, but that actually makes some of the jumpers awkward to reach with my fingers, so this time I'm going to put fly leads on the board and leave the actual diodes to sit beside the PCB in the case, perhaps fixed down with a bit of hot melt glue.

James

[JamesF]

Fly leads for the diodes attached.  No diodes as yet.  I'll cut the leads to length and fit the diodes once I've printed the case and can test everything for size/placement.

James

[JamesF]

And for the final bit of PCB soldering, the MOSFETs and voltage regulator.  The heatsinks I bought turned out to have small steel "legs" on when they arrived, which I didn't initially realise was the case.

I assume they're there so they can be soldered to the PCB and stabilise the heatsink.  And perhaps to connect it to ground.  There's no place for them on the PCB though, so I snipped them off with the side cutters.

Because there's not much room on the PCB for the heatsinks (some of the resistors prevent them from fitting flush with the PCB) I decided it was easier to put the whole thing together before soldering it into place.

Even then it was easier to put some of them into the board at a slight angle to get sufficient clearance.  An alternative might be to just saw 3mm or 4mm off the bottom of each heatsink.  I don't think it would compromise their performance that much.  And again I held them in place with a blob of blutak whilst soldering.  And here they are, all done.

To make much more progress I probably need the case printing, so I'll get that under way.  I'll also go over the back of the circuit board with a magnifying glass just to check there aren't any unintentional bridges in the soldering.  Then I'll plug in the Nano and at least see if it lights up and runs the default "blink" code ok.

James

[JamesF]

I redesigned the lid of the case to have holes for the GX12 sockets instead of the 6P4C sockets and printed it first, then swapped spools for the lower half which is still printing.  Whilst waiting I thought I'd try out the sockets and plugs for size and spacing.  I'm not unhappy at all:

There's plenty of room to allow the retaining nuts for the sockets to be turned and for the screw locks on the plugs to be used, even with my less-than-delicate fingers.  The socket actually came with captive rubber plugs to keep dirt and, more importantly in this application perhaps, moisture, out of the socket when it's not in use, but I've not fitted them for this test (the plugs are held in place by means of a ring that fits under the flange on the socket).

Of course problems may rear their heads as I get further through construction, but so far, so good.

James

[JamesF]

The rest of the case is now printed out, so I fitted the Nano to the PCB and put the PCB loosely in place so I can connect up the USB cable and see what happens.  The good news is that it all lights up as it should and the LED that should flash does indeed do so.

I think it's now time to start fitting all the bits and pieces that will go into the base (fan, USB socket, power socket, humidity sensor).

James

[JamesF]

The Met Office has made the rash promise of several clear nights at the tail end of the week and I'd like to use this if they've managed to get it right so I need to crack on with it now.  This evening has been spent sorting out VAT returns and expenses and I'm working tomorrow evening and Thursday evening so there's not a lot of time left.  Fortunately there's not really that much left to do either.

I did make time to finish off the diodes on their fly leads, covering the exposed leads with plenty of heatshrink.

Once I'm done testing I'll fix them in position out of the way against the sides.

Next step is to fix everything else in the case.  I'll try to get that done tomorrow.

James

[wimvb]

Nice progress. The box looks very deep.

[JamesF]

It is quite deep, I guess.  Unlike (my recollection of) the original build photos I have the LCD display entirely inside the case (which allows the front face to be protected from moisture), so that probably needs about 20mm of case height.  The PCB stands a few mm off the base of the case to allow for the soldered ends of the leads and needs at least 30mm clearance on top of that for the heatsinks and Nano, and then I've left a bit of space in between the two for all the wiring (and because there's not much point having a fan if everything else is squashed in so tightly that there's no easy way for air to circulate).

Having built a couple of these now I think I could come up with a better design for the case that would allow it to be smaller and I may look at that when I build the controller for my travel kit.  I think it would have to have removable ends, as is the case for the one in the build photos.  Otherwise I just can't get my fingers in to work on assembling everything.

James

[JamesF]

In between rebooting lots of servers last night and making sure they'd all come back to life correctly I did manage to make a little bit of progress.  The fan, USB connector, power socket and DHT22 are now fitted.

I drilled the mounting holes for the fan and USB socket through the walls of the case as I wasn't confident that I would get a sufficiently neat hole if I'd 3d-printed them.  For the DHT22 I used a 3-pin connector on one end with a 3-way cable and a 4-pin connector on the end that actually plugs into the sensor itself as it has four pins with no connection on pin 3.

I also found time to make a start on fitting components to the lid.

Having worked so late I went to bed and found I couldn't sleep, so at half three this morning I got up and spent half an hour cutting wires to length for the rest to try to relax :)

James

[arrayschism]

Super thread @JamesF, I'm on with building one of these at the moment. That's a lovely box you've got there - 3D printed at home I take it?

Those diode legs were rather large, as you'd mentioned in another thread. I managed to drill out the PCB with a 1.3mm drill to fit them on the board, rather than having flying leads

Anyway, great job - can't wait to see the finished product!

 

[JamesF]

Yes, I did indeed 3d print the box :)  I was noodling about a bit last night when I couldn't sleep to see if I could make it any smaller, but actually I think the best I can do is to take perhaps 10mm to 15mm off the height.  Whilst the PCB isn't large, the need for space around it for fitting sockets and for the USB plug that fits into the Nano pretty much forces the width and depth of the box to be the size I already have.  That or I'm missing something completely obvious about laying everything out :D

If I'd been building on stripboard I'd almost certainly have drilled out the holes for the diodes, too.  Having them on the board does seem the most desirable arrangement.  As I'm using the prefab PCB I was concerned that there wouldn't be enough of the pad left to solder the lead to if I drilled them out and decided to err on the side of caution.  I will be building one of these on stripboard at some point (only six months or so until we go on holiday -- I'd best get cracking), so perhaps I'd best get some small drill bits in :)

James

[JamesF]

The lid, complete with all wiring.

That's almost all the soldering done.  I think there are just the temperature sensor plugs and possibly a power cable to make up (I think I've run out) that will require more soldering work.

There are a few little gotchas here: the pinouts of the RGB LED at the bottom left, and the display connector at the top right don't match the pinouts of the connectors on the PCB, so I've had to swap the ends around to get the order correct.  The carrier board for the RGB LED was also quite awkwardly made in this instance -- the LED was soldered very close to the board which didn't leave me much room for manoeuvre when connecting the lead so it wouldn't foul the side of the case.  It uses a 90 degree pin header and I ended up bending it with pliers to make it more like 45 degrees.  I assume that's "natural variation" in manufacturing QA, as the first one wasn't that awkward.

And of course, don't do what "a friend of mine" did, and connect up all the GX12 sockets with their nice little caps to keep out dirt and moisture with the caps up the wrong way, then have to undo them all and put them on again the right way around.  I, err, He felt such a fool when he realised.

Now I need to make up all the pin header sockets on the other ends of all those LED, heater and temperature sensor wires.

James

Edited January 15, 2020 by JamesF

[JamesF]

There was one other component I almost forgot!  The DS18B20 temperature sensor that goes on the PCB.  I could have soldered that direct to the board, but put a pin header in instead and mounted the sensor in the plug:

James

[JamesF]

And I've now finished making all the other connectors, so it's time to start testing.  I have already plugged in the 12V supply and the magic smoke didn't come out, so that's a good start.

James

[JamesF]

I've started testing and will post about that in more detail later.  The first few test sketches went well.  When it came to testing the RGB LED and fan however, the fan showed no sign of life.  Not sure what the problem can be there as there's not a huge amount in that part of the circuit.  I've swapped out the Nano and the fan and neither of those change anything.  There is some voltage at the pins for the fan, but perhaps not as much as I'd expect even if it is .  I'll modify the sketch to turn the fan on 100% and test the voltage then.  I guess I should also see between 11V and 12V across ground and the output of D1.  Perhaps that would be the thing to test first.

James

[JamesF]

Hah!  Problem solved.  Resoldered the MOSFET in question and it now works.  Not sure how much more testing I'll get done this evening if the promised clear sky arrives.

James

[brown_rb]

Hi all
I am not trying to confuse things as James posts are very good reading.

I was asked recently about the possibility of adding a 4th channel to myDewController3. It turns out this can be done without much effort. If the FAN is used as a dew controller output this can be done with very minimal effort.

The basics are
1. Wire the FAN output J1 to a dew strap (via RCA connector)
2. Remove the DS18B20 little transistor from J7 and wire J7 to a temperature probe jack (so an external temperature probe can be connected)
3. Load some new 4CH firmware
4. Control the new 4CH box with a new 4CH Windows app
5. No need for RGB LED on J5

With ventilation slots in the project box heat should not be a concern with the MOSFET design. I have done the new 4CH firmware and new 4CH Windows application.

And now, back to James for progress updates.