Non DCC Train Detection

[chaz]

Detecting a train is easy with DCC, but harder with DC. Unfortunately, I'm locked into DC operations. Optical detectors (LEDs) are the most common DC solution. Current sensing detectors are harder.

Here is a prototype (not built yet), DC train detector. It is set to detect currents as small as 20mA (0.02A). It is based on a Hall Effect Current Transducer from ACS.

20mA is the typical current draw of a bright LED. I suggest placing two LEDs as lighting in the last car.

A hall effect device converts current to voltage. Unfortunately hall effect devices are notoriously noisy. The electronics following the Hall Effect device is a low pass filter that limits the noise, and a voltage comparator. More than I wanted, but not excessive. If you go to Digikey and enter the price number, you can find current prices and datasheets.

I've seen discussions about this before, but none of the solutions are as sensitive as this design.

[RCMan]

How many blocks and turnouts do you need?

Dennis

[chaz]

How many blocks depends upon your layout. My layout (that is under construction) has 8 isolated blocks. I want to eventually add signals, so I need to know where the trains are.

I'm going to use a couple of http://www.greensteamproducts.com/Pages/GSP-14.html to control the signals.

My 2.5" x 3.8" printed circuit board holds 4 current sensor circuits...so I need 2 printed circuit boards.

Off topic, but I designed and had printed the bridges and bridge supports.