IRDOT-1D

[Bino]

Hi folks,

 

I've recently purchased 5 of Heathcote's IRDOT infra-red detectors for use in my hidden loops. Having installed the first one, all seemed fine but I noticed that the LED does not always remain lit when the locos are in the isolated section and above the sensor. The IRDOT-1D has a 5 second delay built in and it is around 5 seconds that the LED stays illuminated. Very slight re-positioning of the loco within the isolated section will trigger the LED and it will stay lit but this is not practical in hidden loops.

 

So, does anyone have any advice or suggestions?

 

 

[SHMD]

I had that problem with my home made version of Infra-red Detection.

 

What you have to realise is that the underside of a train is a long mixture of Infra-red reflecting and absorbing materials - at differing heights - and there are even gaps!

Infra-red detectors do work well as motion detections but are much less reliable as block occupancy detectors.

 

Maybe you need to change your control scheme where the Ir-Dot drives a latching relay - to show the siding has been occupied.

Of course this latching relay will then have to be reset somehow!

 

 

Kev.

[richard brown]

Try painting the bottom of the loco/stock with silver paint to reflect the light I have ssen this done on layout using the system

 

Richard

[melmerby]

Try painting the bottom of the loco/stock with silver paint to reflect the light I have ssen this done on layout using the system

 

Richard

Doesn't need to be silver paint, anything shiny normally reflects IR.

A bit of aluminium foil would work

 

How about an IR LED with a IR phototransistor receiver set either side of where the train will be?

Anything it it's way will operate it.

 

Keith

[Suzie]

Bino

 

You need to find a way to 'defocus' the beam so that it illuminates more of the underside of the stock. One or more of the following may help:-

1. Set the emitter and receiver further away from the stock, perhaps make a cone shaped hole under the track and cut away the sleepers to allow the IRDOT to be set lower. It will work quite a considerable distance lower and be more effective.
2. Cut back the heatshrink around the emitter and receiver. It is just there to stop stray light getting directly from emitter to receiver, but sometimes is a bit excessive and narrows the beam too much.
3. Position the emitter and receiver so that light is not reflected directly from the bottom of the stock but at an angle. It seems counter intuitive, but does work sometimes!

[Bino]

thank you all for your suggestions. Food for thought! IRDOT is not the complete solution I thought it would be.

 

I'll post my findings in due course. It may be a couple of weeks!

[Bino]

 

Bino

 

You need to find a way to 'defocus' the beam so that it illuminates more of the underside of the stock. One or more of the following may help:-

1. Set the emitter and receiver further away from the stock, perhaps make a cone shaped hole under the track and cut away the sleepers to allow the IRDOT to be set lower. It will work quite a considerable distance lower and be more effective.
2. Cut back the heatshrink around the emitter and receiver. It is just there to stop stray light getting directly from emitter to receiver, but sometimes is a bit excessive and narrows the beam too much.
3. Position the emitter and receiver so that light is not reflected directly from the bottom of the stock but at an angle. It seems counter intuitive, but does work sometimes!

 

I've gone for the simplest solution which is No.2 in Suzies reply. I've trimmed the heatshrink back as far as I can. The first trimming was an improvement but still gave me some issues.

 

Fingers crossed, all now seems well. No doubt there will be one piece of rolling stock which I haven't tested that will throw a spanner in the works.

 

Thanks Suzie

[PeteDavey]

As previously mentioned, it's much easier to break the beam than rely on a reflection from an inconsistent loco underside, set the two LEDs to coupling height and you will avoid flickering between stock too

[vitalspark]

As previously mentioned, it's much easier to break the beam than rely on a reflection from an inconsistent loco underside, set the two LEDs to coupling height and you will avoid flickering between stock too

 

We are using IR detectors on the new project and had spent some time experimenting using below rail or surface mounted and have also realised that they are not 100% when reflected on underside of locos and stock..however a simple strip of masking tape applied to same cures the issue..alternatively a thin line of white paint also works fine.

Unfortunately we have too much stock to make this practical so opted instead to surface mount the sensors and have them diagonally opposed across the tracks.

This has been fine under test conditions and I have no reason to think it will not prove reliable when applied to the layout.

I made up a simple holder from 1/4" (6.35mm) brass tube which ensures all heads will be at the same height of just under 1" from board level to avoid scatter through the sole bars.

These allow plenty clearance between tracks and are robust enough  to withstand the odd knock.

The new layout is 40ft long with14 fiddle roads each with 6 sections so the idea was to allow the fiddle operators to be assured what roads were available to incoming trains.

As trains move up the bi colour leds used clear from red to green.

The DPDT relays also allow an indication to the front operators if their last road is occupied plus it can open and close berth sections to protect same.

This is all automatic and hopefully will work!!

 

We are making good progress with 'Son of Alloa' as it has become known and I will post more when the work progresses.

Finally I have to say I am impressed with the quality of the Heathcote components and have no doubt they will perform well.

 

Sample brass holder quickly soldered up for test purposes and seems to work ok.

Should be easy to produce and robust and uniform which is important as we need 28 of them. 

 

 

Dave.

[vitalspark]

The above is all in respect of IRDot 3 boards but we are also using the simple IRDot detectors for loco detection in a lye outwith the operators field of vision and for that we have employed below board detectors and as mentioned applied a thin white strip below the units that will use same.

 

Dave.