APR48 Programmer

 

The APR48-3G power supply from Eaton is comparatively cheap and easy to obtain. It is well suited for the operation of power amplifiers up to approx. 1kW.

 

 

The power supply can deliver 1800W. The output voltage is set at 54.5 volts at the factory. The maximum current is 37A.

 

The device is designed as a slide-in cassette for a 19" rack.

 

 

Eaton APR48-3G     Front

Back

 

Modifications

 

In order to adapt the power supply to its intended use, it has been modified as follows:

1.     The connections on the rear for the mains and the DC output have been provided with plug contacts.

2.     The parameters of the power supply have been changed to set the output voltage to 48 or 50 volts.  (see below)

 

 

To accomplish the modifications, the device must be opened. To do this, 9 pop rivets have to be removed. Then the housing can be opened and the electronics removed.

 

 

Once the work has been completed, suitable hexagonal press-fit nuts can be inserted into the frame instead of the drilled-out pop rivets. With max. 6mm long screws, the case can be neatly closed again.

 

 

 

 

Reprogramming the power supply

It is not possible to adjust the output voltage or other parameter of the power supply in an analogue way, e.g. via trim potentiometers. However, various operating parameter of the APR48-3G can be adapted to the intended application by changing data. This especially applies to the output voltage and current limiting. The corresponding parameters are stored as data records within the microcontroller of the power supply. It is therefore necessary to read these data from the EEPROM of that MC, make the desired changes and finally transfer the data back.

 


The programming of microcontrollers usually requires special programming devices and suitable software. This technique is not entirely trivial in terms of installation and operation. In addition, the purchase just for this purpose is usually not worthwhile.

 

That's why I've developed a small programmer that doesn't require any special hardware or software. It is connected to a PC via a serial port (USB) and handled with an ordinary terminal program, e.g. PUTTY.

 

The connection to the APR48 is made via the 6-pin SPI interface. The Power Supply is disconnected from the mains during programming.

 

 

Quick Start Guide  (PDF-Document)

Details on how to use the programmer are summarized in the Quick Start Guide.

 

 

 

The technical documentation (BOM, Schematics)  are stored as PDF files.
The design was created with Diptrace V4 .

 

I will provide the firmware of the programmer as HEX code on request.

 

Ready-to-use programmer with SPI cable

 

and CP2102 communication module.

 

 

 

 

Update: 14.11.2023   DB8BH

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