Hi All At the moment I use a Hornby elite to run my Railway(Ho scale) but would like to build and use a Dcc++ base station and jmri. I have the uno and motor shield on order but have a question my elite supplies 15v 4amps to the track what is the maximum power I can supply to the shield can I use the elite power supply also the shield specs says 2amps per channel max 4amps total. If only the main track is being used and nothing on the program track is all 4amps available on the main also what is the max amps at 15v that I can safely supply to the shield Regards paul...
Assuming you are referring to the Arduino Motor Shield R3 (what is shown on the DCC++ web site) or a compatible clone, the max amps you can draw from a channel is 2amps. Even if you don't use the programming channel, the max on the main channel is still 2. The DCC++ Base Station code has current sensing to keep you from trying to draw too much current and damaging the motor controller board. You can use the power supply that you have, you just won't be able to use its full current-providing capability. If 2amps isn't adequate, you could look at alternate motor controllers. Or if you are going to set up power districts, use boosters (there are some DIY options, such as the one on Dave Bodnar's site).
Hi Mike, Thank you for the info, I was worried I may damage the motor shield using a 4 amp power supply, I will only be running 4-5 dcc sound enabled locos (oo gauge) at a time I think the 2 amps should be more than enough. The arduino and shield arrived today so will get it all connected up with the layout and see and as you say if not adequate then I will take a look at Dave`s site on the power booster. Regards paul
Just to add; as said you can use a higher current rated PSU than 2 amps. By default the DCC++ setting when using a std R3 Motor Shield will limit the maximum current drawn to approx 0.9 Amps per track. In use, if the track power keeps tripping off you can gradually increase the trip current setting by changing the value of CURRENT_SAMPLE_MAX in the file Currentmonitor.h. and reinstalling the software. The value of CURRENT_SAMPLE_MAX by default is set to 300 and this equates to a trip current of 300 x 2.95 mA = 0.885 Amps. With the standard motor shield you should be able to increase this value to no more than 650 which equates to 650 x 2.95 mA = 1.92 Amps, though if you do set it this high I suggest you do initially check the Motor shield when in use to make sure it doesn't get too hot.
