Retirement Sale: Save An Additional 20% Off of Our Normal Discount Price
On Most Items - Excluded Items are Highlighted in Orange

Click here for the list of remaining items.

The information in this section is general in nature. More specific information is provided in the listing for each block detector or signaling system. This overview is only to provide a broad knowledge of detector types.

Block Detection is needed for prototypical signaling, but signaling isn't the only reason to do block detection. One could use block detection for automatic turnout or route control, animation operation, to indicate whether or not a staging track is empty (signaling to the operator, but not signaling per se), or various other things. Each purpose for detection, and various methods of achieving those purposes, can and do require different types of detection.

A detector has two components: sensing and reporting. There are three basic type of sensing and two types of reporting.

Current sensing can be done with diodes or with an inductive coil, and is used for district (block) detection needed for prototypical signaling and other uses that require the operating device to know when a train is anywhere in the detected block.

Diode-type detectors generally reduce track voltage by 0.7 volt. This means that if you aren't detecting every block, you may have to install "dummy" diodes, or use other methods, to even out the track voltage. Inductive coil detectors sense current flow without reducing voltage, but generally cost more. This type is not as readily available as the diode type.

Train sensing can be done with photo cells for spot detection. This can be used to operate signals in a non-prototypical manner, and to make various types of layout animation work when a train crosses a certain spot on the track. A good example of this is grade crossings.

Detection reporting is either via LocoNet or direct. LocoNet-reporting detectors are for things that will be controlled by computer, the command station, or other LocoNet-controlled signaling systems or devices. Direct-reporting detectors are used to control the signaling systems, signals, or other devices directly.

Following is a list of block detection types we carry:

If your goal is signaling, you have to decide how you want your signals to work before you can determine how your layout will be blocked. Refer to the Signaling Overview for that information. Once you have your signaling system worked out, you can decide which type of block detector to use, and how to block your layout.

Obviously, locos, lighted passenger cars, and cabooses draw power so will be detected by any reasonable current-sensing detector. But freight cars, many of which have plastic wheels, do not.

If you want a freight car to be detected, it must have at least one truck with metal wheels and an appropriate resistor to draw enough current for your detector to see it. The resistor value depends on how sensitive your block detector is. Each manufacturer recommends resistance for their detectors. While resistances lower than recommended will work, resistances higher than recommended shouldn't be used unless you know there is tolerance for it. For example, Logic Rail's signaling systems sensitivity is set for 100K ohms, but they recommend 15K-ohm resistors for freight cars. Because of the extreme sensitivity I'm sure 20K ohms will work quite well. Hobby Gauge detectors, for example, need about 4.7K ohms, but 5.1K should also work well.

The more resistance you can use the better. For example, 4.7K ohms on 300 cars will draw close to 1-amp. But 5.1K ohms on the same 300 cars will draw only about 0.8-amp. While this isn't really much difference in the scheme of things, if you use 1K-ohm resistors, as recommended for Hobby Gauge HGE when used on a DC analog system, the same 300 cars would draw 4.5 amps - quite a bit.

One last note: with many block detectors, it requires more current to make the block detector see the load to start with, but less current to keep it being seen. While 5.1K ohms may be needed to "trigger" the block detector, 10K ohms may be enough to keep it triggered. If you know there will always be at least two freight cars on a siding, 10K can be used on each car to trigger a Hobby Gauge, for example, while 30K to 40K can be used on each car with Logic Rail.

Adding resistance to a freight car requires metal wheel sets. We carry Jay-Bee for this because they also have metal axles. While most of Jay-Bee's wheel sets come without built-in resistors, they do offer two wheel sizes with various resistance values: 5.1K, 10K, 20K and 39K. While Logic Rail recommends 15K, 20K should work just fine - considering sensitivity is set for 100K. But if you don't have hundreds of cars to do, using 10K won't hurt a thing.