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Micron MR001b 2.4GHz DSM2/DSMX Receiver

This document is regularly updated and the most recent version may be found online at http://micronrc.uk/mr001b where you will be able to view larger versions of the images.

MR001b Bottom

MR001b Top

The MR001b receiver is well suited for use in large scale live-steam or battery powered locos. It operates on 2.4GHz using the Spektrum DSM2 or DSMX protocols; thus it works just like any other DSM2/DSMX receiver but includes some useful features for model railway control. The MR001b is small (30x18x11mm) and space for it is easily found in most locos.

The MR001 family of receivers includes two hardware variants:

• single extended aerial and manual bind (requires jumper plug for bind)
• two extended aerials for diversity reception (the receiver takes data from the aerial with the strongest signal) and auto bind (receiver goes into bind mode 5 seconds after failing to find a transmitter signal)

and two firmware variants:

The MR001b free-air range, when used with a Micron low-power transmitter, is 40m-50m and approximately 200m when used with a full-power (100mW) transmitter. This range will be reduced indoors due to absorption by furniture / fittings and reflections from metal surfaces. Range is also reduced if the receiver aerial is in a metal enclosure. Ideally, the aerial should be placed outside the vehicle body and clear of any metal. The 30mm active tip of the extended aerial needs to 'see' the transmitter so should be placed through a hole in the loco body - e.g. into the cab space. The MR001b aerial should not be cut short or made longer as this will affect operation of the receiver. It is important to perform a range check after installation to ensure you have full control of your loco at all positions around the layout.

MR001b can be powered from a battery of 3.45V up to 8V; use of a 4 or 5 cell NiMH rechargeable battery or the 5V regulated output from a speed controller is typical.

The standard configuration has servo outputs on P1 to P5, front/rear lighting on P6 and P7 and a channel 3 switched output on P8:

Other configurations can be supplied to special order at no additional cost.

MR001b has 2 LED indicators, one on the top near the aerials and another on the bottom, these are labeled 'LED RF' and 'LED CPU' on the diagram below. There are actually 2 LEDs on the bottom, but only one of them is used.

RF LED:

indicates when a good signal is received, flashes rapidly when the rx is in bind mode and flashes slowly if the receiver power was interrupted

CPU LED:

indicates the receiver status:

• flashes slowly after switch on an waiting for a good transmitter signal
• lights continously when a good R/C signal is being decoded
• flashes twice, pause and repeat when the receiver is deselected (see Loco Selection)
• used for feedback when setting servo travel end points or reversing servo direction

When used with a Micron model rail transmitter, throttle is on P1/ch1 controlled using the large speed knob and direction is on P3/ch3 controlled using the toggle switch. The Micron transmitter should ideally be configured for low-off throttle with no centre detent and a non-biased direction toggle switch. When used with an aeromodel type stick transmitter, throttle is controlled using the throttle stick and direction is controlled by the elevator stick. Servos, plugged into MR001b P1 and P3, are linked to the regulator and reverser. The battery can be connected, via an on/off switch, into any of the unused pins.

Battery Powered Loco

An Electronic Speed Controller (ESC) that supports forward and reverse should be connected to P1/ch1 as shown in the diagram. The MR001b is powered from the ESC 5V output.

The resettable fuse is essential to protect the battery in the event of a ESC or wiring fault. The switch must be capable of carrying the maximum motor current; if a suitable mechanical switch cannot be found, an electronic switch should be used instead (contact Micron for details).

Any of the Micron model rail transmitters can be used or a Spektrum compatible stick type transmitter. Tx21 and Tx22 transmitters have an inertia control which gives a more realistic acceleration and deceleration by slowing down the rate at which the throttle channel is changed.

To bind a receiver, it is switched on with no transmitter active (for normal operation, the transmitter should be switched on before the receiver).

Manual Bind

Some variants of MR001b support autobind where the receiver automatically goes into bind mode approx 5 seconds after switching on with no pre-bound transmitter active. If autobind is available, this will be indicated on the receiver label. All variants support manual binding.

manual bind:

The large jumper plug supplied with the receiver is connected across the signal pins (top row) for P5 and P7 and then the receiver is switched on. If fitted, P5 servo and P6/P7 LEDs must be removed when manual binding.

auto bind:

The receiver enters bind mode approximately 5 seconds after power-on if it has either never been bound or it fails to find its bound transmitter. It is not necessary to remove the plugs for P5 servo or P6/P7 LEDs when using auto-bind.

Bind mode is indicated by a rapid flashing of the receiver RF LED and the following steps should be followed to bind with your transmitter:

1. transmitter switched off
2. if Loco Selection is enabled, move the transmitter loco selection switch to the required position
3. switch on the receiver in bind mode (manual or auto)
4. only when the RF LED is flashing rapidly, hold down the transmitter bind button and switch on
5. wait for the transmitter to indicate that it is in bind mode and then release its bind button (the power LED on Micron model rail transmitters will flash when binding)
6. after a short delay, the RF LED should stop flashing and go dark and, after another 4-5 seconds, both RF and CPU LEDs will light and stay on
7. the receiver is now bound to the transmitter

The implementation of Loco Selection in MR001b is fully compatible with the Deltang Selecta feature and uses R/C channel 2 by default. When Loco Selection is enabled, the controlling R/C channel (e.g. 2) may still be mapped to a servo output but, of course, this will not change as the transmitter switch is rotated.

The receiver has a 800ms delay when the transmitter Selecta value is changed. This is to avoid obeying the transmitter while the Selecta switch is being moved - e.g. a receiver on Selecta #4 should not change any outputs while the transmitter Selecta switch is moved from #3 to #5.

Loco Selection Toggle

MR001b is normally supplied with Loco Selection disabled. To toggle whether Loco Selection is enabled or disabled:

1. turn off the receiver and transmitter
2. put the large jumper plug on signal pins (top row) for P4 and P6
3. switch the receiver ON and the CPU LED will display
   • 1-flash if Loco Selection is disabled
   • 2-flash if Loco Selection is enabled
4. remove the plug and the CPU LED will display a rapid flash until the receiver is switched off

MR001b has an on-board 3.3V regulator and 220 ohm resistors in series with the signal pins so limits the LED current to approximately 12mA. The LED should be connected between the signal and negative pins (top and bottom rows).

The default setting is for the LEDs to follow the throttle channel with 'centre-off' and is appropriate for a battery loco with ESC. For live-steam use, the LED behaviour can be reprogrammed for 'low-off' and this uses full-range throttle on ch1 and directional control on ch3.

Set Throttle Type

To toggle whether the directional LEDs operate as 'centre-off' or 'low-off':

1. turn off the receiver and transmitter
2. put the large jumper plug across signal pins (top row) P3 and P5
3. switch the receiver ON and the CPU LED will display:
   • 1-flash for low-off
   • 2-flash for centre-off
4. remove the plug and the CPU LED will display a rapid flash until the receiver is switched off

1. turn off the receiver
2. put the large jumper plug across signal pins (top row) P1 and P3
3. the CPU LED will flash once per second
4. remove the jumper plug
5. the receiver will reset and the CPU LED will flash rapidly until the receiver is switched off

Other jumper settings are used to change servo direction and alter the servo travel end points (see below).

1. select the servo output to be adjusted using the small jumper
2. reverse the servo using the small jumper, or increase or decrease the servo throw using the large jumper

Reversing or end point adjustment can be performed as many times as required on the selected servo. When complete, remove power from the receiver to stop, all changes are stored to the CPU memory. The next time power is applied, the receiver will operate normally.

Only one servo output can be changed at a time, the method must be repeated for each servo that requires adjustment.`

WARNING: never place the small jumper across the positive (middle row) and negative (bottom row) pins. This will short the battery.

Step 1 - select servo output to adjust

Select P1 to adjust

Servo outputs are on P1 to P5. The small jumper plug is used to select one of these outputs for adjustment, it is placed across the wanted signal pin (top row) and the adjacent signal pin. For example, to select P1 (throttle), place the small jumper plug across signal pins 1 and 2 as shown in the image (the black connector in the image is the battery plugged into P4).

The servo output is now selected. Jumper plugs are used on P6 and P7 to reverse the servo or adjust the travel end points. Reversing or end point adjustment can be repeated as often as desired while the servo is selected. To stop the process, remove power from the receiver.

Step 2 - adjust selected servo output

The selected servo may now have its direction reversed or have the travel end points adjusted:

Reverse servo direction

Reverse direction of P1 servo

The small jumper plug is placed across signal pins (top row) for P6 and P7 to reverse the servo direction. The image shows a servo plugged into P1, a battery plugged into P3 and the small jumper across P6/P7.

The servo direction will reverse each time the procedure is executed.

Adjust servo travel

Decrease throw

Increase throw

The servo travel end points can be increased or decreased using the large jumper plug on P6 (decrease) or P7 (increase). The adjustment is done in small steps every ½ second and the CPU LED flashes for each step. To make an adjustment:

1. move the servo to the low or high end using the transmitter control
2. use the large jumper to make changes:
   • on P6 to decrease the throw
   • on P7 to increase the throw
3. either remove the jumper or move the servo away from the end to stop the adjustment

The CPU LED will stop flashing and the servo will stop moving when the adjustment limit is reached.

• The limit for decrement is the mid point of travel so, if an end point is decreased to the maximum amount, there will be no servo travel in that direction when the transmitter control is moved.
• The limit for increment is the maximum signal value. Take care: not all servos will respond to the maximum range of servo signal values; stop decrementing when the servo stops moving even though the CPU LED is still flashing.