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[ Electrical Division : Traffic Lights ]

Created by [ Sidharth Baveja], last modified by [ Sarvath Sharma] on Nov 04, 2020

Considering buying this controller for the traffic lights. 

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This is where the circuit for the AC Traffic Light controller we have at the moment: http://galakelectronics.com/VG-305.htm?keyword=traffic+light+controller&x=0&y=0&and=on and http://galakelectronics.com/VG-307.htm

The data sheet for the actual 12-Inch Traffic Signal: http://www.econolite.com/wp-content/uploads/sites/9/2016/10/signals-12poly-datasheet.pdf

Data Sheet for the AC Traffic Light Controller: https://www.galakelectronics.com/instructions/VG-307B%20Instructions.pdf

More can be found here: https://www.econolite.com/products/signals/

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[Research on the Traffic Light]

-During the mech-electrical integration meeting on May 29 2020, we considered replacing the original Galak controller (which combined control logic signals and the power output) because of secure mounting concerns. There were two main concerns:

-Was suggested during meeting to replace board with a generator. This should give the Galak board’s output of 120VAC, max 4.2A (the Galak is fused at 5A). Galak also gives min 4W, max 500W to each individual light.

-Wall outlets usually provide either 120VAC or 240VAC. There are step-down transformers on Amazon (https://www.amazon.ca/Voltage-Transformer-2000W-Power-Converter/dp/B07CCLSXJB/ref=sr_1_6?dchild=1&keywords=voltage+transformer&qid=1591131238&sr=8-6 ) that go up to 2000/3000W.

-Cheap, thinking about breaking down a power cable that plugs into this transformer (and solder/crimp the ends of the power cable to a really thick PCB). PCB can be designed to handle lots of screw pressure.  

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Brainstorming and concerns for traffic lights (checking with Ardhendu from mech):

-Generator box could fit into a sleeve or rectangular enclosure, either on the top or bottom of the temp. traffic light mount here: https://drive.google.com/file/d/1G8bb3ghnCerhUdC2kI3EnqoEL1lwGWmL/view?ts=5ed1a95f

-Recommended for generator to sit at bottom for easy ON/OFF access, plus it can't fall that way. A reason to put the generator at the top is for our extension cables from generator<=>controller PCB to be more manageable during assembly because they'd be shorter

Info needed:

1) Dimensions of internals of traffic light enclosure. How big can our PCB be? Another concern is that there probably wasn't meant to be anything mounted inside of that, so would be hard to find manufacturer data for how strong the plastic is (if, for instance, we mount PCB to one of the "fins" running along the inside).

2) Can we have an oddly shaped PCB? (Going to research who can do this) The light enclosure has fins that might need a really weird PCB shape

3) Thickness of PCB - I'm gonna run some calculations by mech to see what we need for really strong screw/belleville-washer pressure. Also going to check PCB manufacturer's max thickness and if they do special orders

4) Controller to light wires - controller-side can be screwed on, but main concern is how traffic lights themselves terminate... did they come with wires again? If so, how well are those secured

5) If our PCB takes the 120VAC from the transformer, there'd be electrical parts sourcing (massive MOSFET as switch? Might have heat dissipation issues, could try to imitate Galak layout...) and logic. How many modes do we want? There'd be standard "auto" with a set time, maybe also want wifi-controllable manual mode for convenience...

6) How did we mount the traffic light enclosure onto our temporary arm? Is there extra room for external PCB? (If we decide not to stick PCB inside enclosure, biggest reason I can think of is space)

7) Waterproofing board? Or at least stick it in plastic bag within the enclosure? Is rain even a concern, because the enclosure should be standardized to prevent weather damage...

8) On the temporary arm pic (link above), it looks like we aren't even using the yellow original traffic enclosure I remember from last year. This just affects the PCB mechanical interface, not really important for circuit design, so if we still don't know about the arm but sure about the PCB for secure connection reasons we can go ahead...

Mounting Ideas

For mounting, there are 2 options Ardhendu brought up. He also mentioned there was already a PCB (the Galak I'm guessing) with the traffic lights right now. I don't think it was mounted, but it would be good to check - if it's mounted, maybe we could imitate that with our new PCB.

+—-+——————————–+——————————–+ | Mo | Dowel through PCB holes; | Use thermal tape to stick PCB | | un | dowels are mounted to | onto light unit's flat | | ti | enclosure | backside | | ng | | | | St | | | | yl | | | | e | | | +====+================================+================================+ | Pr | -Heat dissipation was | -Really easy to do - literally | | os | anticipated to be a big issue | just stick the PCB on. We can | | | if we use a MOSFET with high | design the PCB to have | | | current and high voltage, so | physically portruding parts on | | | if we "dangle" the PCB in | only the front side | | | midair with dowels, there's a | | | | lot of air space around it | -We can use strong glue | | | | between PCB and light backside | | | -There's a bunch of | after to make it very secure | | | mechanical ways to make sure | | | | the PCB sits snug on the dowel | | | | (this "dowel" could be a | | | | threaded steel rod, which we | | | | can use locking nuts on, etc.) | | | | | | | | -We can adjust the wires | | | | before or after mounting the | | | | PCB inside | | | | | | | | -If traffic lights themselves | | | | get warm/hot from using a lot | | | | of current, this would give | | | | airflow space between PCB and | | | | light, rather than sandwiching | | | | them together in a hot packet | | +—-+——————————–+——————————–+ | Co | -Mounting dowels to an | -Kinda a permanent solution. | | ns | enclosure is hard unless we | If we want to really secure | | | drill a hole into the | the PCB, taking it off will | | | enclosure and just fill the | mean damaging something | | | gap with sealant or | | | | something... | -Not as good for heat | | | | dissipation, because the | | | -If we use 3D-printed parts to | thermal tape would channel the | | | hold dowels to enclosure, | heat into the plastic backing | | | it'll be a pain to get and | of the light, which might not | | | test (printing centre shut | be rated thermally. Do they | | | down). Also not that strong | even give data for this? | | | unless we use a lot. If no | | | | airflow inside enclosure, | -If we use screwed-down | | | it'll sag from heat + | fitting between wires and PCB, | | | pressure (depends on material | then we'd have to do that | | | though) | before sticking/gluing down | | | | PCB. (lack of flexibility when | | | -Probably need to modify | assembling, also can't remove | | | enclosure itself to accomodate | wires and reattach after PCB | | | dowels | stuck on) | +—-+——————————–+——————————–+ | Ot | -Need info on space + possible | -Need info on available | | he | mounting locations inside | surface area of traffic | | r | enclosure. Not even sure what | light's backing | | no | dimensions are important | | | te | because I have no idea what | | | s | the inside looks like, so I | | | | don't have mounting ideas | | | | that require certain | | | | dimensions. Just use | | | | discretion? | | +—-+——————————–+——————————–+

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Circuit (Pending OKR for using PCB+transformer to power light)

-Use 3 thick power MOSFETS that use a microcontroller signal. Heat dissipation is issue; Ardhendu recommends using capacitor (since it's AC-powered) to maximize efficiency.

-Maybe solid-state relay instead of MOSFET? Compensates for short lifespan of mechanical relays, I'm not too sure about heat. Sources say loads over 4A require heatsink, but is it better than MOSFET? https://www.eurotherm.com/en/solid-state-relay-installation-hints/

-Components table:

Component Reason for adding ——————- ————————————————— Capacitor AC efficiency; voltage smoothing (although transformer's internal circuit should handle voltage stability for 120VAC power)

MOSFET Control high voltage, high current flow

Microcontroller Signal logic

Wifi/BT receiver Taking remote instructions to switch light mode. (Trying to use IR to penetrate enclosure is kinda sketchy)

Button/switch Useful for misc. functions like hard ON/OFF, debugging?

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Looking at pre-made controllers

-Planning to keep looking at premade controllers because of impedance between wires, cross-talk, etc. between AC wires, which makes designing a circuit really tedious.

-I looked on Amazon, Digikey, Mouser and Aliexpress. None of even the large selection of boards on Aliexpress don't use thick PCBs, or screw clamping mounts for wire termination - I think it's just too specific of a criteria for it to be mass-produced like that. During my first coop, we had a lot of large custom PCBs built in-house, and the few times I recall seeing a screw-on clamp termination was for very large bolt sizes (At least ~M6) where the wire was also very thick, given that it was a power line.

-I think we'll have to settle for buying something with the Galak-style screw terminal mounts, maybe desoldering the terminals to replace with something else (but this requires us to get our hands on the PCB and see if it's feasible anyways, so that's a question for later.) If we're concerned about the wires being shaken loose, I'd recommend fixing the length of wire that just protrudes from the PCB termination, so the range of motion is limited. (Maybe hot glue, although if heat is an issue - which I didn't calculate - we could drill holes into the enclosure's side and use some cheap, common wire management clamp to bolt down the wires.)

-For fixing the PCB itself, something I've done with good success is using a thick sheet of firm, hard plastic (in the neighborhood of 5-10mm thick, depending on how long our bolts are). This sheet had holes drilled to match the PCB's holes, and was sandwiched between the PCB and the enclosure. We'd then bolt down the PCB normally, and then fill the gap between the plastic and the PCB with hot glue to make a really solid foundation. If heat is an issue, we could try a more heat-resistant filler and plastic sheet to spec, although it's a ghetto method anyways and it would just be better that we try out the hot glue first to estimate whether it can hold up or not. Given that the transistors appear to be only on one side of the PCB, that helps too. When I mounted a PCB this way during coop, I didn't run into problems, but the PCB did not dispel lots of heat the same way we expect this one to.

-I looked into some controllers and found a nice compact one that's similar to the Galak. I'd estimate the surface area is about a third/half of the Galak one, which is nice for flexibility in mounting inside the enclosure. The first link is the normal board, and the second link has an RF remote control operating up to around 100m:

  1. (44 USD)    https://www.trafficlights.com/controllers/n3-ryg-light-controller/
  2. (150 USD)    https://www.trafficlights.com/controllers/rcn3-remote-control-traffic-signal-system/

They have a lot of options on their website (Some are 24V DC rather than 120VAC though).

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After some extra re-search we found two more AC Traffic Light contollers that were programmble:

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  1. (104 CAD) https://www.amazon.ca/Channel-Light-Controller-programmable-Control/dp/B07JD3ZH3M/ref=pd_sbs_147_1/141-0368917-5209638?_encoding=UTF8&pd_rd_i=B07JD3ZH3M&pd_rd_r=5cde55fa-c369-442d-930a-29d7c1dafe33&pd_rd_w=45F9Q&pd_rd_wg=PcDCU&pf_rd_p=51202c9a-f9ab-4d97-ad76-aa53f0391454&pf_rd_r=696CRAA499MH9NDZNHXS&psc=1&refRID=696CRAA499MH9NDZNHXS
    1. This is an Arduino module but the only issue is that it works for a 3 stage traffic light system. We could possibly get two of these and program them to control all 6. 
    2. OR we could use another Arduino module to extend the applications of the first one onto all 6 Channels 
    3. Works for a 100V-240VAC 50Hz-60Hz 3 Channel System
  2. (NO Price given) https://www.amazon.com/Controller-Sequencer-6-Channel-Programmable-Crosswalk/dp/B00OEISVTQ
    1. This model is similar to the one from the original one we want to replace (same manufacturer)
    2. Upside is that this is fully programmable and seems to fit the necessary requirements. 
    3. Works for a standard 120VAC Line Voltage (240VAC is availble per request)

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Attachments:

blue_light_schematic.sch (application/octet-stream)
blue_light_schematic.brd (application/octet-stream)\

Document generated by Confluence on Nov 28, 2021 22:40

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