Monday, 22 May 2017

Back to the Dew Heater Controller

Well its been a funny old day, wonderful sunshine one moment, torrential rain the next. So during the rain, ive been hidden away in the workshop.

A project thats been awaiting further work is the Dew Heater Controller. Having picked up a box for it at the Blackpool rally, it was about time I cracked on with it!

The Dew Heater bands come with phono plugs on them, and as the temperature sensors can be operated in two wire mode, and the phono panel sockets come in red/black pairs, i'd already decided to use phonos for all the control connections

The DHT22 humidity sensor, which provides the environmental monitoring needed to establish the dewpoint values, was the first component to be installed, as it needed to go on the outside of the box. Held down with an M2.5 nut and bolt, its legs pass into the case via a row of 1mm holes. Once complete, these and the sensors base will be sealed

A 2.1mm DC Jack for the main 12V supply was fitted at the opposite end to the sensor. This is the right hand side (sensor on left). The three pairs of phono sockets then fit on what will become the 'top' or 'back' of the box, depending on how you think of it!

One of the most important tasks was to decide where all the various internal modules would fit! The photo below shows the three MOSFET driver modules, and the OLED displat module, placed where they would eventually reside

And after a lot of measuring, drilling, filing, checking, and remeasuring etc, the OLED can be seen fitted. Here it is under test with just the Arduino Nano controller

The arduino is mounted on a bit of Perfboard, and hot-melt glued into the corner. In this location it is still possible to easily connect a USB lead to power it for testing, and for later software upgrade if required. Ive used up a lot of left over ribbon cable that was just kicking about, so lots of coloured heat-shrink on the connections!

In this second to last photo, the majority of the work is done. All the modules are glued in place, each of the MOSFET drivers has been tested, using a temperature sensor tag soldered to the first input phono! (the TO92 package you can see).  All that remains is to complete wiring up the 2nd and 3rd sensor channels, the control outputs to the MOSFET modules, the 12V supply lines and the outputs to the three heater channels.

A final going over with a pencil eraser will be needed to clean up the front panel.

I also have a 40m CW transceiver, a JJJ Electronics v.1, on the bench belonging to Bob M1BBV.  He obtained this ready built but in unknown and unfinished condition from a Silent Key sale. Well, it at least works, after a fashion. Its a little unstable but should be fine once the board is cleaned up and reworked. A number of parts need to be properly seated. I'll post some pics of the work on that later.

No comments: