The comparator detects, hence, a short positive pulse with the increase of the voltage. 11mV higher.īy a change in voltage on the lower network needs clearly needs a longer time to follow the input. Normally the voltage on the negative input of the comparator is approx. The voltage drop is fed to different RC networks. This rise causes in the sense input of the programme a voltage drop. This happens by the fact that the current is raised for a short time by 60 mA. 30-60mA (depending on the capacitor's value).Īccording to RP 9.2.3 a locomotive decoder in service mode should send back an acknowledge signal. The idle current thereby rises, however, around approx. The resistors (R3 or R4) should have a maximum dissipation of 1 W. C10 should not be chosen higher than 200nF because, otherwise, after the polarity change of the DCC signal the short circuit detector will react. It has been proved that a combination of series resistor and parallel capacitor with the values of R3=R4=0,15 Ohm and C9, C10=100nF to 200nF will give good results. These can be avoided or reduced if one filters the output, in addition, by a RC combination.
The signal overshoots are caused due to reflections on the rails.
Should still signal overshoots appear on the track, nevertheless, the additional RC combination can be redimensioned (larger capacitor). The output is compensated inside with a RC combination to avoid signal overshoots. Possible induction of the source signal on other circuit parts (e.g. In principle the track connection is made by means of twisted pair in order to avoid Track output, snubbernetwork on the output signal The voltage drop at this resistor is used for the ACK detection. Over a current measuring resistor (0.5 ohms, parallel connection of two 1 ohm resistors). On the programming track additionally the current reversal from the rectifier bridge is led This is adjusted by means of the resistors R7 and R12.Ī value of 39k allows a short circuit current of approx. The rectifier bridge driver has an integrated short-circuit monitoring circuit The external S88 input is protected by means of a polyfuse against short circuit. RECOM R-7805-0.5 in SIP3 package (this is a plug-in replacement for 7805). With an efficiency of 85% this circuits is able to deliver 2,5A. In the case that more S88 outputs are used, the current drawn from the 5V will be too high for the 7805, and a switching regulator type PTH08080 from Texas Instruments can be equipped on the board. Instead of this power supply connector, also screw terminals can be used on the board.
Here the interior pin is plus, the outside is minus. Unfortunately there are different versions of plugs on the power supplies. On X13 (X2) a stabilized 15V-voltage of an external power is fed and used for the supply of theĭual full bridge driver L6206 and the 5V of the positive voltage regulator 7805. (F_CPU in config.h and/or in the Project Setting). If the program is recompiled, the correct clock rate must be absolutely indicated The ATmega is clocked with 16 MHz, this is also the main frequency from which all other timing is derived.
I recommend ATmega644P, evern if there is no xpressnet. This processor has a 32kByte Flash programme memory, 2kByte SRAM and 1kByte EEPROM,Īlso an interrupt controller, timer and I/O "on chip". The heart of the openDCC is formed by an AVR ATmega32 or ATmeag644P (required for Xpressnet) from Atmel. : Booster, DCC and programming track output : ATmega, +5V power supply, JTAG and programming interface OpenDCC - A Command Station for DCC - Curcuit Description Schematic, Allocation of pages
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