QSX (PEARS) Power Supply now powers the GRHub Network 145.550Mhz RF Link Radio.

Recognition :  Al Akers ZS2U,  Andre Botes ZS2ACP and Bryan Haefele ZS2BH (SK)

An article by Al Akers ZS2U describing a power supply appeared in the June 1993 issue of Radio ZS.  The circuit, to which a fourth 2N3055 has been added to enhance the current handling capability.

In addition to this ZS2CP has produced a circuit board which incorporates an over voltage protection circuit adapted from n article by the late Brian Haefele ZS2BH in QSX Newsletter of April 2000.

The original article, schematic diagram, PCB outlay and component outlay can be downloaded by clicking HERE.

I constructed this power supply in early 2001 and it has run flawlessly for the past 20 years.  This power supply is now connected to the GRHub 145.550 Mhz RF Link Radio and also powers 2 x Fan Controllers discussed on this Blog.

I opened the power supply this past Friday to clean the inside and to fit a auto fan controller to run the fan. (Not shown in the images.)  I have tested the fan controller installed to the power supply.  It works great and even reduced some of the fan noise considerably.  

With both the radio and power supply now fitted with a automatic fan controller, it is really an "assurance of mind" that I do not have to manually switch fans on and off.  As the temperature rise it switches on automatically and once the temperature falls below a set level it switches off automatically.  Fingers crossed that the fan controllers do not fail which could destroy the radio or the power supply if they overheat. I however do have a plan in mind to inform me should they fail.

Here is a few diagram images of the power supply.  Images of the fan controller is also available on this Blog. Just click on Fan Controller in the Labels column.

Images:  (Click on images for larger view.)

UPDATE 3: Keep the GRHub Radio's and Raspberry Pi's cool

  I recently constructed the second 741 Op Amp Thermal Cooling Fan Controller for the power supply of the 145.550 Mhz RF Link Motorola Radio.  This one has an adjustable pot to control the thermistor's reaction time .  Previous posts on this Blog describe how this circuit function and operate.

Once again a money saving hint due to the unavailability of rubber grommets.

I  purchased 4 round insert plugs (16mm x 4) for R8.23.   Grommets are far more expensive while the courier costs are more than the components.  All I did was drilling a hole in the center of the plug, the size that just allow the wires through.  Simple and cheap and works like a charm.

Here is a few photos of the completed project.

Power Outage 18 October 2022 Heiderand, Mossel Bay

 The notification underneath refers: 

Although the GRHub Network has a fully back-up power system the power outage is the ideal opportunity to upgrade the back-up and main power systems of the GRHub Network.  A new 100 Ah battery will be installed as well as several power down converters.  I envisage that the Network will be off line and off air for 2 - 3 hours on 18 October 2021.  The power outages might be an inconvenience but on the other hand gives me the time to do upgrades to enhance the operation capability of the GRHub Network.

UPDATE 2: Keep the GRHub Radio's and Raspberry Pi's cool

  Just a short update on the 741 Op Amp Thermal Cooling Fan Controller.  I must say I am quite impressed on how this simple little circuit/project is performing.  Thus far it has run/operated perfectly.  It keeps the Motorola Radio cool.  Very little heat is present on the heat-sink even with long-winded conversations/broadcasts of more than 1 hour.  I spoke to my brother in law OM Nico ZS4N  over the weekend.  He ran one of the fan controllers on the then Aliwal North repeater for more than 5 years without any problems.  Today that very same controller is running in his Shack.

During a discussion on the SARL Forum mention was made of the LM358 Op Amp used in a thermal cooling fan controller project.  Well I have decided to build the 358 fan controller.  This fan controller also uses an output relay so it can basically switch/connect to any system to warn of an emergency, run as a fan controller, light source or sound device. I will start working on this fan controller soon and will provide feedback on its functionality.

I also intend to modify the current 741 Thermal Cooling Fan Controller currently used on the 145.550 Mhz link radio.  The modifications will provide me with the following:

• Led indicator when the fan is running (RED)
  
• Led indicator when the fan is not running (GREEN)
  
• Install a variable 10K trim-pot that enables me to adjust when the fan must turn on at different temperatures.

Another option also in the back of my mind is to use a timer for fan control. I am going to connect the timer to the radios PTT for logic control and the timer will fire a relay that runs the fan. The fan will run while in TX and then 10 mins after last PTT.  Underneath is the timer I will be using.  More on this project in a future post.

 Back to the workbench and lets see if I can build and modify the Thermal Cooling Fan Controller.

UPDATE 1: Keep the GRHub Radio's and Raspberry Pi's cool

 The fan controller found a "home". (project box)  Now this enclosure is more than 20 years old.  I dug it out of the junk box.  It once housed a transistor tester which I constructed.  The enclosure is build out of double sided PCB.  Those were the days when copper clad PCB was still cheap.  Today it will be an expensive venture to build a PCB enclosure.  A little sanding and a cote of spray paint and it is as good as new.  Herewith a few images of the fan controller installed.  The only thing that needs to be done is to attach the thermistor to the radio heat-sink and then I can activate the 145.550 RF link.

Thermistor installed on Motorola Link Radio

Top view of the thermistor installed on Motorola Link Radio

Finally:  You can ask me many things but do not ask me to install a project in a project box/enclosure.  I hate it!!  It is a time consuming venture even if you find the correct size enclosure.   Maybe it is time that I should invest in a 3D printer to print my own project boxes.  Who knows Christmas might come early this year.