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The loco-receiver 81210 (750 mA)

Its power output is max. 750mA. It has the following features:


These loco receivers run on all digital systems that follow the NMRA DCC rules, as e.g. Modeltreno Digital line (INTELLIBOX), Lenz, Roco, LGB, Digitrax, System One etc.

The Arnold Digital loco receiver runs also on the Märklin (Motorola) format and new extended data format Digital System (not on conventional AC!).


Before installing

Test the current consumption of the loco in normal DC operation. At full power and blocked wheels it must not exceed 75OmA. Be sure that there are no electrical connections between the motor inputs and the wheels or the chassis.


Connecting the motor

First connect the black wire to the contacts of the left wheels and the red wire to the contacts of the right ones. Then solder the orange wire to the motor input that has previously been connected to the right wheels and the grey wire to the motor input formerly connected to the left wheels. Put the loco onto the programming track-section and read out the loco address. lf the programming device (e.g. the Modeltreno Intellibox) detects the address (factory default is 003), the receiver is wired correctly. Now you can try a short run of the loco in order to be sure that it runs in the direction the loco control indicates. lf the running direction is wrong, please swap the orange and grey wire at the motor inputs.


Wiring the headlights

The white wire feeds the headlight when the loco is running forwards and the yellow wire feeds the headlight at the opposite side. Connect these two wires to the bulbs of the headlights.

(Fig. 1 shows the wiring in case of bulbs that have no electrical connection to the chassis).

(Fig. 2 shows the wiring in case of bulbs that are placed directly inside the chassis and therefore have an electrical connection to one of the rails).

On locos equipped with a white and a red headlight you can combine the white light on one side with the red one of the other side. The receivers can feed both lamps by the same output.


Tests and short-circuit detection

The loco receiver is equipped with an on board short-circuit detection preventing damages to the decoder itself. A test is continuously done and the receiver reacts very sensitive even to small and short overloads. If a short-circuit or an overload occurs, the loco is stopped at once. In this case please take the loco off the rails and search for the problem (Wiring ok? Motor inputs still connected to the chassis or wheels? Wire damaged?). If the error is not corrected the loco wili stop ever and ever again.



Make the testing of the loco without cars. Climbing up a grade or with a big load applied, the short-circuit detection stops the train even if the wiring is well done. In case there's a short-circuit between the motor inputs, the loco doesn't run at all, but the headlights blink. After some testing when no short-circuit detection has stopped the loco, you can reduce the continuos detection by programming the CV49 (see below), in order to make effective the short-circuit detection only when the loco starts or the layout is powered on. Only with the reduced short-circuit detection you can operate the loco with heavy load and in hard grade; otherwise the short-circuit detection will stop the train ever and ever again.



The loco receiver can be set-up to fit the features of the prototype locomotive and the mechanical facilities of the model loco. This is done by an electronical programmation. The receivers we produced before, were programmed by writing into directly addressable registers. The programmation of the new features of the receivers would be too complicated by registers. So the programmation by configuration variables - abbreviated CVs - was introduced.

Address, minimum speed, acceleration and deceleration delay (momentum) can be programmed by registers or CVs. The additional features can be programmed only by CVs.



CV/REG feature possible values defaults
# 01 address 001-119 003
# 02 minimum speed 000-255 000
# 03 acceleration delay 000-255 002
# 04 deceleration delay 000-255 004


CV feature possible values default
# 05 top speed 000...255 255


The CV 29 is a memory that keeps the state of some important features of the loco receiver. Calculate the sum of the values, resulting from the list below, that you want to program and write the sum into the CV 29 (default is 004).


CV feature values  
#29 sense of running 0 = normal 1 = inverted
  27/28 speed steps 0 = 27 speed steps 2 = 28 speed steps
  analogic-detection 0 = not allowed 4 = allowed
  speed-ramp 0 = calculate 16 = read from CV 67 ... 94


you want to program the following features: normal sense of running (= 0), 28 speed steps (= 2), analogic detection allowed (=4), speed ramp from table (= 16); the sum is 0 + 2 + 4 + 16 = 22; write 22 into the CV29.

The CV49 operates another set of features of the Arnold loco receiver. As before calculate the sum of the values you want to program and write it into this CV

CV feature values  
CV49 load compensation 0 = on 1 = off
  short-circuits-detection 0 = always 2 = at start
  data storage 0 = on 4 = off
  digital/analogic operation 0 = digital 8 = analogic
  Motorola-format detection 0 = on 16 = off

In case of problems due by dirty track or dirty wheels, it's a good idea to switch off the Motorola - format detection.

The CV5O in digital operation determines the load compensation. A low value causes a fast compensation to the load changing; a high value causes a slower reaction.

CV50 width of pulses for motor 000 ... 025 default 020

Important: if you select an unfortunate value, there can occur mechanical resonances (inconstant speed). The value 020 has proved, during our tests, to be a suitable programmation for this feature.

In DC operation this CV controls the width of the pulses of the current feeding the motor, therefore the top speed of the train.

How to program the loco receiver

You can change the address of the loco and any programmation of the registers by Modeltreno Intellibox. The programming devices of other manufacturers can program the loco receiver 81210 too, if they work along the NMRA rules.

You will find the way of programming in the instruction booklet of the Modeltreno Intellibox

lmportant : the loco receivers delivered in Germany must be programmed to run on a DC layout by indicating the DC - operation via the CV49 (see above). This makes the loco run only on DC - layouts. If you want to come back to digital operation, then you re-program the loco to digital service by changing the CV49 once again.

Running on Märklin Digital

The Arnold loco receivers can run on a Märklin Digital (Motorola data format) layout. They understand the old and the new extended format.

Important : you can't program the loco by the Märklin devices because electronical programming is not supported by the Märklin system. Your dealer will program the receiver for you using the Modeltreno Intellibox.

You must not run an Arnold digital loco on conventional AC layouts.

15/02/2008   by  MODELTRENO