Hi guys: In my HO layout, I will command the switches with servos, driven by a robotics board, an Arduino. Besides that, another Arduino board will produce the DCC signals (this is already working). Now, has someone used 20+ servos in a layout? Thanks.
Not on an Arduino all running from the same 5V supply, but small groups of servos connected to DC servo decoders that produce their own 5V supply locally work fine. The big problem with servos is that they tend to draw a lot of current at switch on because they all try to move at once. Twenty servos running from a single supply is going to take over 10A or so for a brief period, and if the voltage builds up slowly the period of current draw will be extended and there will be a lot of twitching. The commercial servo accessory controllers only do four to eight servos per unit for good reason.
I set up a DCC booster for my Tam Valley driver boards and servos. It's a 5A booster, and it powers 3 Tam Valley Quad boards and 11 servos without any problems. If I someday add more servos I'll add another booster. - Jeff
I don't know if you've seen this before, but Geoff Bunza shows how to run 17 servos from a $3 Arduino Pro Mini board. http://model-railroad-hobbyist.com/node/19446 Steve S
