The "MoAT" Project Throttle.

Published:2013/6/7 21:34:00 Author:muriel | Keyword: The "MoAT" Project Throttle. | From:SeekIC

The third schematic is a throttle that was built for the London Model Railroad Group because of a quest for more power (amps) to triple head an all brass 21 hopper coal drag with scratch built Steam locomotives. A quest ranking somewhere between that for the Holy Grail and the Golden Fleece. The fact that the transformer (22 Volts and 15 Amps) that powers this throttle just happened to appear at the right time helped get it off the ground. As the schematic shows this design uses two silicon controlled rectifiers that are triggered through a special SCR trigger transformer. This transformer allows the cathodes and gates of the SCR's to be isolated from the control circuit and thus permitting the incorporation of the over current protection into the throttle. The SCR's form half of a rectifier bridge that provides the track power while the two diodes in the bridge module that the SCR's replace supply power only to the PUJT and the control circuits. In effect the power flow through each SCR's is halved because each is triggered on every other cycle of the full wave DC. The current limiting simply bleeds the charge off of the memory capacitor if the voltage across the 0.05 ohm resistor rises higher than the voltage at the plus input of Ic2. The voltage across this resistor is directly proportional to the current through it (E = I X R). The level of limiting is adjusted by the 10K ohm potentiometer.



Reprinted Url Of This Article:
http://www.seekic.com/circuit_diagram/Basic_Circuit/The_MoAT_Project_Throttle.html

Print this Page | Comments | Reading(3)