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Akkuload - a microprocessor controlled loader for accu cells

Changes

Changes on May 2, 2005

In version 1 of March 2005, a serious bug causes a false calculation of the load current. The load current is roughly half the value than is selected and displayed. To avoid this bug, download the new version of akkucalc.asm as of May 5, 2005, re-assemble and re-program. (Thanks for uncovering this bug to Sebastian Mazur).

Description

The acculoader loads up to four single accu cells with predefined currents between 5 mA and 220 mA (max. up to 350 mA in a single channel). The characteristics and all necessary parameters are selectable for each of the four channels separatly, so that mixed loading of different cells is possible with no limitations. The load characteristics are preselected, the microprocessor measures and controls currents and capacities. The control over the loader can either take place with a serial RS232 interface and a terminal program like Hyperterminal or by three keys. Output and control uses a 4-line-LCD.

The characteristica and the load history of up to 32 accumulators are storable internally, so that the necessary parameters (load capacity, currents, etc.) can be selected very quick. The number of full loads with nominal capacity is stored and automatically updated each time a load ends.

Using the RS232 interface, all informations are readable and all functions can be performed. By using the monitoring mode all measured values are traced and can be copied to a textfile. These values can be used to display the load characteristics via PC software.

Load curve

Functions

Akkuload uses an ATMEL AVR ATmega16 at an internal clock of 8 Mcs/s. Attached to the processor are:

four pulsewidth generators for the control over the load current,
four outputs for initiating the unload cycle,
four AD converter channels for measuring the accu cell voltages,
four AD converter channels for measuring the four load currents,
three inputs for the keys, in part combined with
four LED outputs for signalling the loading state of the channels,
two serial ports (RXD/TXD) for communication over the RS232 interface,
10 Port-In- and Outputs for control over the LCD display, combined with
four in- and outputs for the In-System-Programming-Interface.

Download

Hint: the switch schematic in the 2005 version had a bug in the wiring of channel 3. This is corrected in the below refernced version of 2007.