Which Decoder?
Please note that this page has been superseded by updates.
The decoder can be made in any one of four flavours! 8-output high power 3-output high power 8-output low power 3-output low power
To summarise the differences between the versions.
High power - Can drive up to 300mA per output at full track voltage against the blue wire. Outputs can be on or off. Outputs are suitable for driving bulbs, smoke units, couplings, motors or anything else that you would normally connect to the function output of a decoder. Total decoder load should not exceed 2A. The main advantage of this version is that it can be used anywhere that is ‘DCC ready’ and has a decoder socket. Outputs are not overload protected.
Low power - Can drive up to 25mA per output at 5V (most LEDs only need 2mA to 5mA for normal brightness). Load can be connected between output and 0V or output and 5V or both (single output will drive both headlight and tail light for example). Bi-colour LEDs can be driven by connecting them between a pair of outputs (ideal for class 121 bubble cars etc. where head and tail light are in the same lens). Total decoder load should not exceed 90mA. Main advantages of this version are that it can be made smaller and there will be less heat dissipated, there is the potential of more efficient use of the outputs and more efficient use of the function buttons when driving complex lighting scenarios (such as the class 170 example with day and night lights as well as parking). This version will provide constant brightness of the LEDs regardless of track voltage (even when running on DC once the track voltage gets to 5.5V). The low power outputs are the same as the extra outputs C and D on the Zimo MX620 (or E and F on the MX63/64). Outputs are overload protected.
The choice of decoder should be made based on the following:- Q. Will I be connecting the decoder to a NMRA/NEM decoder socket? If yes use a high power output decoder. Q. Will I be driving 12V devices? If yes use a high output power decoder. Q. Will I be driving LEDs? If yes use a low output power decoder as preference, but either will do. Q. Do I want the lights to be constant brightness when running on DC? If yes use a low output power decoder and use LED lighting. Q. Do I want to do complicated lighting with LEDs? If yes use a low output power decoder. Q. Do I need to drive more than 25mA? If yes use a high output power decoder.
The differences between the versions is minimal and there is no reason why some of the outputs on a high output power decoder cannot be configured for low power by just leaving off the output transistor and replacing the current limiting resistor with a more suitable value.