[Dr_C2]

I traced out the motor/brake drive circuits for both the C8515 rev H and the above new C7005 (ver 11/2022). Both have identical topology (i.e. same schematic) and both have the same motor drive transistor (DMN3404L).

Both, therefore, will have very similar motor drive capabilities - with just one minor difference due to the differences of layout and size of the PCBs. For SOT23 packaged devices (i.e. the three pin package used for the DMN3404L) the maximum safe operating current is a function of the heat sinking properties of the PCB including its layout and size. That said the difference should be quite small in this case.

Allowing for a small safety margin a sensible limit for motor current is 4A for both the C8515 rev H and the C7005 ver 11/2022.

For cars running on a track both decoders should be fine even for higher torque motors such as the NSR King 21 EVO (350g-cm) at 12V. But note the stall current at 12V is 8A so in the scenario of a full power stall the MOSFET will fail before the motor windings become damaged.

For medium torque motors such as the Slot.it V12/4 23k (170g.cm) the same of course applies for cars running on the track at 12V i.e. they should drive OK. For this motor the stall current at 12V is 3.5A so typically the decoder will remain undamaged even for a sustained motor stall. However, in this stall scenario damage to the motor will result - it will be dissipating 42W.

I guess folk will have different views on which it is preferable to replace… a motor or a MOSFET?

Of course the real answer to the question is to avoid motor stalls :)

i.e.

- keep the track clear of foreign objects which could get trapped inside and jam the motor.
- avoid holding the wheels locked when powered up
- avoid snow ploughing through crash sites
- avoid using motors which are damaged and draw excess current

With these precautions both the C8515 rev H and the new C7005 should be fine with medium torque motors (e.g. V12/4) and higher torque motors (e.g. King 21 Evo).

I don’t plan to test either of these decoders or motors to destruction (I’ll leave that to others), but I will run cars with both types of decoder and with both types of motor and report back.

c