Hi,
I'm trying to develop a very simple traffic light system for a private single-lane road that is about 300m long, and would like some feedback/advice/ideas as to making this work as simple as possible please. I've come up with a basic circuit design that is attached to this post, involving a power source (owner wants it to be solar panels, I'm thinking probably a 12V system then?), red bulb/light, PIR sensor and relay at each end of the road.
The basic logic from my design is:
- Car approaching PIR at TOP end of road activates sensor
- PIR 'Out Signal' then travels down to relay at BOTTOM end of road and switches the relay
- Relay at BOTTOM switches. This completes the bulb circuit (lighting red to stop any traffic coming through), but opens the PIR circuit, therefore not allowing that PIR at BOTTOM to activate
- When the timer on the activated PIR at TOP of road finishes, the 'Out Signal' goes low again, de-energising relay at BOTTOM of road, bringing whole circuit back to normal state where either of the PIRs can be activated
Please, any help on general design, specs required, suggestions about voltage drops over 300m, power source, etc. etc. would be massively appreciated!
DIY Traffic Light System
DIY Traffic Light System
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Re: DIY Traffic Light System
Good on ya for taking this job on! It sounds like fun.
u should make it solar powered.
make it so the sensor shuts off the battery, so it saves up when your not near the traffic lights.
But what is the sensor actually going to be? that could proove a hard bit.
mechanical relays would do fine for a simple job like this, transistors end up complicating issues i hate their guts.
i recall being at the trainstation and seeing the relay box!
I dare u to make all the relays yourself!!! thats doing it like a real man, from complete scratch this job is completely possible.
u should make it solar powered.
make it so the sensor shuts off the battery, so it saves up when your not near the traffic lights.
But what is the sensor actually going to be? that could proove a hard bit.
mechanical relays would do fine for a simple job like this, transistors end up complicating issues i hate their guts.
i recall being at the trainstation and seeing the relay box!
I dare u to make all the relays yourself!!! thats doing it like a real man, from complete scratch this job is completely possible.
Re: DIY Traffic Light System
Thanks.
It's my son who posted this but it's my lane. I've thought for a while that simple outdoor solar powered garden lighting PIR activated with adjustable sensor so that it works in daytime would be OK but I've struggled with how to connect / get message from one lane end to other with a simple circuit breaker / maker.
My son designed what appears to work but what I don't understand is what type / size of relays I will need at each end and how I interconnect within the garden lighting if integral units are used or can I source separate PIR and lights units.
For cost purposes, I have also worked on using easily available indoor telephone cabling carried in old black / blue water pipe down side of lane as this would seem cheap and safe because of no dangerous currents. Radio signal is out because of bends in lane and a hill in the way.
I have assumed from his logic and flow chart here that the same PIR activated could trigger a separate relay at same end same end to then show a separate Green / go light being on for same time as the red at top because it's timer is running from same PIR timer?
I think that it's the current flows / cabling needs and relay units that are our sticking point so really will appreciate feedback of any of those matters.
It's my son who posted this but it's my lane. I've thought for a while that simple outdoor solar powered garden lighting PIR activated with adjustable sensor so that it works in daytime would be OK but I've struggled with how to connect / get message from one lane end to other with a simple circuit breaker / maker.
My son designed what appears to work but what I don't understand is what type / size of relays I will need at each end and how I interconnect within the garden lighting if integral units are used or can I source separate PIR and lights units.
For cost purposes, I have also worked on using easily available indoor telephone cabling carried in old black / blue water pipe down side of lane as this would seem cheap and safe because of no dangerous currents. Radio signal is out because of bends in lane and a hill in the way.
I have assumed from his logic and flow chart here that the same PIR activated could trigger a separate relay at same end same end to then show a separate Green / go light being on for same time as the red at top because it's timer is running from same PIR timer?
I think that it's the current flows / cabling needs and relay units that are our sticking point so really will appreciate feedback of any of those matters.
Re: DIY Traffic Light System
I don't know about how much volt drop you'd get over that sort of distance on something as small as telephone wire, it may be you need some sort of electronic amplifier in there to overcome this.
Re: DIY Traffic Light System
A fascinating project. There are a few things I think you need to think about before it becomes one that is reliable, and will work 24/7/52.
1. I am not sure that solar panels will be the best solution for this project - they will need to top up a battery (to provide power at night), and work during the day sufficiently even in the depths of winter.
2. For the design I think you should settle on a standard 12v supply. Most PIRs are powered from 12v, suitable 12v relays are cheap and readily available.
3. Decide on the type of lights at each end (Led, incandescent, high power LEDs and so on. The type of light could have a major impact on the power supply design.
4. Consider what happens when vehicles of different speeds go in each direction along the road. I think it would be a good idea to use the PIR at one end to signal that a car has entered the one-way part, and the second to signal that it has come out. You would need a failsafe, which could be by the PIR timing longer than the slowest vehicle - in other words, the system will always reset.
5. Yes, it is easy to incorporate a green signal - in your diagram just connect a light from the NC relay output to the supply. This may have an effect on the power supply design, as two of the lights will always be lit.
6. I can see some problems with using PIRs as the sensing agents - they will need to be set to pickup the passage of a car, but not a cat. They will need to work in full summer daylight with the same degree of reliability as they would in darkness. You may have stray deer or sheep which would almost certainly trigger them, hence my reference in point 4 of making sure of an automatic reset.
7. The resistance of the ordinary type of telephone wire in general use is of the order of 100 - 150 ohms/ km, and therefore should not be any real impediment in its use. If necessary, you could always double up the wires.
8. All in all, I think you could with advantage consider having all the logic at the home end, and powered from the mains. The logic could be powered from one of the plugin power supplies, like the type which charge phones (but 12v, of course). These usually can supply decent currents - up to 1A or so - which should be more than enough for your project.
Hope this helps.
1. I am not sure that solar panels will be the best solution for this project - they will need to top up a battery (to provide power at night), and work during the day sufficiently even in the depths of winter.
2. For the design I think you should settle on a standard 12v supply. Most PIRs are powered from 12v, suitable 12v relays are cheap and readily available.
3. Decide on the type of lights at each end (Led, incandescent, high power LEDs and so on. The type of light could have a major impact on the power supply design.
4. Consider what happens when vehicles of different speeds go in each direction along the road. I think it would be a good idea to use the PIR at one end to signal that a car has entered the one-way part, and the second to signal that it has come out. You would need a failsafe, which could be by the PIR timing longer than the slowest vehicle - in other words, the system will always reset.
5. Yes, it is easy to incorporate a green signal - in your diagram just connect a light from the NC relay output to the supply. This may have an effect on the power supply design, as two of the lights will always be lit.
6. I can see some problems with using PIRs as the sensing agents - they will need to be set to pickup the passage of a car, but not a cat. They will need to work in full summer daylight with the same degree of reliability as they would in darkness. You may have stray deer or sheep which would almost certainly trigger them, hence my reference in point 4 of making sure of an automatic reset.
7. The resistance of the ordinary type of telephone wire in general use is of the order of 100 - 150 ohms/ km, and therefore should not be any real impediment in its use. If necessary, you could always double up the wires.
8. All in all, I think you could with advantage consider having all the logic at the home end, and powered from the mains. The logic could be powered from one of the plugin power supplies, like the type which charge phones (but 12v, of course). These usually can supply decent currents - up to 1A or so - which should be more than enough for your project.
Hope this helps.
Re: DIY Traffic Light System
My thoughts to get things underway so you can improve on the design later.
1. you can put the cable into a hosepipe for protection.
2. instead of a detector at each end, you can use a pneumatic push button [this will also give you the timer function to hold the relay on for up to 10 mins or so ]
3. from this point on I would go with David's ideas and keep the current in the circuit to about 1 amp,so this could mean LED'S.
4. you may be able to experiment with garden lights as they have the necessary components, and to use a LED shining on the photo cell [even with a bit of shielding ]
to hold the relay off until the button is pressed.It may be required to rehouse the components of the garden lights,and upgrade the batteries.
5. RS Components part list.Cable 411-817, 12 volt relays 351-572
6. this needs to be bench tested first and tweaked.
1. you can put the cable into a hosepipe for protection.
2. instead of a detector at each end, you can use a pneumatic push button [this will also give you the timer function to hold the relay on for up to 10 mins or so ]
3. from this point on I would go with David's ideas and keep the current in the circuit to about 1 amp,so this could mean LED'S.
4. you may be able to experiment with garden lights as they have the necessary components, and to use a LED shining on the photo cell [even with a bit of shielding ]
to hold the relay off until the button is pressed.It may be required to rehouse the components of the garden lights,and upgrade the batteries.
5. RS Components part list.Cable 411-817, 12 volt relays 351-572
6. this needs to be bench tested first and tweaked.