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More Ideas MR204

MR204 Latching Relay for Momentary Switch

The relay used on the MR204 is rather unique. It has 2 coils for energising the contacts, or rather one coil to energise them and one coil to de-energise them. This means that a momentary pulse on Coil 1 changes the state of the contacts, and they remain in that state until Coil 2 receives a momentary pulse.
It also has 2 sets of 'changeover contacts' which mean you can switch 2 separate circuits at the same time, with a rating of 2 amp per set.

<img src="MR204.jpg" alt="MR204 Momentary Switch memory PCB">
<img src="MR204 Specification.jpg" alt="MR204 Secification">
MR204
Some Applications:
There are dozens of applications for this product in your Layout here are just a few.

Points Control with Control Panel Indication
<img src="Points Control.jpg" alt="Points Control with Control Panel Indication">
Application
PDF
In this application the MR204 is used to control a Point Motor, a Signal, and 2 LED’s at the Control Panel. The switch is a Momentary action Mini Toggle Switch, (this can be replaced by 2 mini Push Button switches).
Ideally the MR204 should be fixed near the set of points it is controlling, as the Signal will also be in the same area.
If you are using a Positive & Negative Bus Bar - the toggle switch and the LED's only require a 6 core back to the control panel.
If you are not using Bus Bars then you will require a 8 core cable back to the control panel
The colour code for the wiring is 0v Black, +v Red, please see the individual product instruction sheets to see the colour code they are using.
The relay has latching contacts, this means once energised and power is removed the contacts stay in that state until the second coil is energised.
Once you have the system wired as above, you may find the indicators are back to front, this is due to the state of the relay when you first switch ON. In this case you may have to swap 2 & 3 around.
R1 is a 1K quarter or half watt resistor placed in the negative line to the LED's, to reduce the current drawn by the LED's
Using the MR204 with a CDU in the System
There is no problem using the relay card in systems with CDU's. However the CDU must not be used through the relay contacts, only to drive the relay coils. The reason for this is because when the contacts seperate as the relay changes state, this will create a small spark, eventually this will burn out the contact plates.
Please note the polarity of the output of the CDU, the positive must go through the switch and then subsequently to the coils of the MR204 relay.
Use the auxillary power supply to power the equipment that you are switching through the contacts.


<img src="CDU in the system.jpg" alt="Using MR204 with a CDU incircuit">
Home & Distant Signal Control
Application
PDF
<img src="Home & Distant Signals.jpg" alt="MR204 to Control Home and Distant Signals">
In this application the MR204 is used to control a Point Motor, a Home Signal, and a Distant Signal. The switch is a Momentary action Mini Toggle Switch, (this can be replaced by 2 mini Push Button switches).
Ideally the MR204 should be fixed near the set of points it is controlling, as the Signal will also be in the same area.
You will require a 2 core cable back to the control panel
The colour code for the wiring is 0v Black, +v Red, please see the individual product instruction sheets to see the colour code they are using.
The relay has latching contacts, this means once energised and power is removed the contacts stay in that state until the second coil is energised.
Once you have the system wired as above, you may find the indicators are back to front, this is due to the state of the relay when you first switch ON. In this case you may have to swap 2 & 3 around.
Automatic Forward / Reverse (Shuttle)
<img src="MR204 Shuttle.jpg" alt="MR204 used in automatic Forward and Reverse Shuttle">
Application
PDF
In this application the MR204 is used as a Automatic Forward / Reverse (Shuttle) Control. Sensor 1 and Sensor 2 could be placed anywhere on a loop, or even back to back. The train will run from Sensor 2 to Sensor 1, when it passes sensor 1 the circuit will change the polarity of the tracks putting the train in reverse. The train will now travel in reverse until it passes over sensor 2, at which time the MR204 will again change the polarity of the track putting the Train into forward again.
This will continue until power is removed from the system.
By adding a toggle switch to the 0V line from the Auxiliary Power Source you can disable the MR204 so the polarity remains the same.
Please note there is no slow down or slow start up facility in the MR204, so the train will have it's power Reversed at whatever speed you have set the Train Speed Controller.
Connecting power to the rails can be done in a number of ways, most proprietary manufacturers have their own rail connectors, or you can solder wires directly to the underside of the tracks.


Station Stop with Manual Override
Application
PDF
<img src="Station Stop MR204.jpg" alt="MR204 used in Station Stop Application">
In this application the MR204 is used as a Station Stop with Manual Override. As the Train passed over the sensor the MR204 cuts power to the rail and the train will stop.
You must insert 2 Isolating points as shown. The critical point is how far from the left Isolator do you place the Sensor. Too close and the train may over run the Isolator and just continue. Too far and the train will not stop at the station. So there is a little trial and error until you find the correct  position.
The Push Button changes the state of MR204 and allows power back on the track so the train can move forward.
Replacing the Push Button switch with a timer will give an adjustable stop period, see other circuit for the wiring of a timer.


Running Lights Control
Application
PDF
<img src="MR204 Running Lights.jpg" alt="MR204 used in Running Lights Application">
In this application the MR204 is used to control the signals after a train has passed, each MR204 informs the next MR204 of the status of the last signal. This allows a cascade effect so each signal shows the correct aspect at all times. It is however limited to 2 aspect signals.
As the train passes over Sensor 1 the MR204 will change state which in turn changes the Signal 1 from Green to Red. Also an indicator back at the control panel if required. At this time Signal 2 should be at Green as should all signals left of this.
When the train passes over Sensor 2, Signal 2 will change from Green to Red, and Signal 1 will change from Red to Green. This effect will continue as the train passes over the next sensor and so on, until it gets back to Sensor 1 where the cycle will start again.
The distance between Sensor 1 and Sensor 2 will be dependent on the size of your Layout, it could be every 300mm or 500mm and so on.


Automatic Points Switch
Application
PDF
<img src="Point Control MR204.jpg" alt="MR204 used in Automatic Point Control">
In this application the MR204 is used to control a Point Motor automatically. The MR204 is controlled by 2 Reed Switches (Sensor 1 & Sensor2) this means the Locomotive requires a Magnet fixed to the underside of the unit to activate the Sensors.
This can be used on systems where the fiddle yard is feeding into a Main Line. The Sensor 2 is activated by the Loco switching the points to straight through, the MR204 now removes power from the sensor so any subsequent passes over the sensor have no effect on the Point Motor. The points will remain in this position until Sensor 1 is activated.
As a Train passes over Sensor 1 the points will change and power will be removed from Sensor 1, and put back on Sensor 2. Further Trains coming from the sidings will have no effect on the points.
With this arrangement there is one spare set of contacts on MR204, this can be used to drive a signal set, isolate the track, give an indication back at the control panel, or block another set of points.
The relay has latching contacts, this means once energised and power is removed the contacts stay in that state until the second coil is energised.
Once you have the system wired as above, you may find the indicators are back to front, this is due to the state of the relay when you first switch ON. In this case you may have to swap 2 & 3 around (you will only have to do this once - after the initial wiring, after this it will always be correct)


Siding Occupied Indication
Application
PDF
<img src="Siding Occupied MR204.jpg" alt="MR204 used in Siding Occupied">
In this application the MR204 is used to indicate back at the Control Panel if a Siding is Occupied or not. As the train passes over the Reed Switch the indication changes from Green (Siding Clear) to Red (Siding Occupied). When the train leaves the siding it passes over the same Reed switch which will change the relay back to Green on (Siding Clear).
The second set of contacts on the relay are used to change the function of the Reed switch, in effect converting it into two separate switches.

A second circuit can be used in conjunction with this first circuit to Isolate the track (so the train enters the siding and then power is removed from the track stopping the train) and controlling the Points with an indication back at the Control Panel as to the status of the points.
Automatic Forward / Reverse (Shuttle) with Timer:
Application
​PDF
In this application the MR204 is used as a Automatic Forward / Reverse (Shuttle) Control. Sensor 1 and Sensor 2 could be placed anywhere on a loop, or even back to back. The train will run from Sensor 2 to Sensor 1, when it passes sensor 1 the circuit will change the polarity of the tracks putting the train in reverse. The train will now travel in reverse until it passes over sensor 2, at which time the MR204 will again change the polarity of the track putting the Train into forward again.
This will continue until power is removed from the system.

You could now add a timer into the system so that the Train stops somewhere for a predetermined period. It can be anywhere, where the sensor is placed.
The Sensor for this is marked 'Station Stop Timer Sensor' this activates a timer which cuts power to the track, thereby stopping the Train at that sensor position.
Wires 'H' & 'G' where going to the track, now they go to the COM on the Timer relay. 'M' & 'N' wires go from the relay back to the track. M&N must be connected to the NC (normally closed) contacts on the relay as shown.
The Train Stationary time is adjusted by turning the preset on the timer board. Please see the separate instruction sheet for the MR350.
By adding a toggle switch to the 0V line from the Auxiliary Power Source you can disable the MR204 & the MR350 so the polarity remains the same, and the timer is OFF.
  
Below is a range of sensors available:
<img src="Sensor Selection.jpg" alt="Selection of Sensors from Brimal Components">
Sensors
Sensor 1. SL919. Single Pole Changeover Proximity switch. End on operating distance 5mm. Diameter 6mm, so can be very unobtrusive coming through the baseboard.

Sensor 2. SL926. Single Pole Normally Open Proximity switch. Operating distance 8mm, size 22mm Long, 3.5mm wide, 4.2mm high.

Sensor 3. SL927. Single Pole Normally Open Proximity switch. Operating distance 8mm, size 15mm long, 3.2mm wide, 4.2mm high.

Sensor 4. SL923. Single Pole Normally Open Proximity switch. Operating distance 10mm, size 10.5mm long, diameter 1.95mm. Drawback is that bending can break the glass and therefore the switch.

Sensor 5. SL928. Changeover Contacts Proximity switch. operating distance 10mm, size 14.0mm long, diameter 2.5mm. Drawback is that bending can break the glass and therefore the switch.

Magnets 6. SL932 & SL933. Neodynium Magnets 6mm & 3mm diameters both 2mm thick, with North marked with a dot.

Sensor 7. SL700. Infra Red detector with Transmitter & Receiver built into the one unit. It does require an electronic circuit to operate it. visible size 10.2mm long, 5.8mm wide, 7.2mm high.

Sensor 8. SL710. Infra Red Transmitter. It does require an electronic circuit to operate it, and will require a similar unit as the receiver. visible size 5.0mm diameter, 8mm high.