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Thread: Build your own switchback - turn/running flasher controllers

  1. #41
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    You should check out McMaster-Carr. It is a US
    company but I checked on couple web sites who members
    live in canada and they got shipments w/o any
    problems. They have EVERYTHING!!! Give them a call to check.
    330-995-5500. Also look at web site.

  2. #42
    Senior Member Frank818's Avatar
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    I've asked McMaster twice in the past 3 years and they don't deliver to residential addresses outside USA. Only commercials. It's not clear on their website which is why I asked twice, just in case they changed mind.
    But that's ok, I have still some tire repair rubber cement, I'll use that.

    Will start dismentling the Eagle Eyes later this week or next w-e (as soon as I get my new soldering iron). I expect 6 to 10h of work on these.
    Frank
    818 chassis #181 powered by a '93 VW VR6 Turbo GT3582R
    Go-karted Aug 5, 2016 - Then May 19+21, 2017
    Tracked May 27/July 26, 2017
    Build time before being driveable on Sep 27, 2019: over 6000h
    Build Completed Winter 2021

  3. #43

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    If you make your own PCB using toner transfer process, don't forget to use paint or some app to mirror the image before you print your toner paper. ...

  4. #44

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    If you are assembling from my pictures and drawings - please take note. Q2 the BS170 transistor comes in different packages. Some have a flat face, round back side (TO-92 case style). Others have a larger flat face and a smaller flat back instead of round. The drawing that shows parts layouts, shows the top looking down and the rounded side of Q2 faces away from Q1 - this is the correct orientation.

    With the round back it is easy to identify the front/back. And the numbers are printed on the flat side. With the large flat and smaller flat back, the numbers may be printed on the back side, which can lead you to install the transistor backward.

    The photograph of my boards shown above are built with the confusing transistor style, with the printing on what would normally be the rounded side the TO92 style case. So my transistor as shown in the photo has the back facing up (with the numbers visible).

    If you have the TO92 style BS170 with a flat on one side only, then you need to mount the transistor with the flat facing down, where you will NOT see the printed info on the part.

    A forum member found this out for us the hard way... I'm so used to these parts it didn't cross my mind to cover this before.

  5. #45
    Senior Member Frank818's Avatar
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    Quote Originally Posted by aquillen View Post
    The clearance between the solder points and the inside of the aluminum housing is almost zero
    Mines aren't made of aluminum, they are full plastic, including the inside. I guess I got a different version and that I am immunized against possible shorts.

    Plus, the wire that comes out of the housing is glued with some kind of silicone or black glue that makes the wire very tight in place and won't really move. I know yours do.

    Also the lenses were very glued in place and only way to remove them was with a lot of heat and quite some force with a small flat screwdriver, before it would cool down.
    Frank
    818 chassis #181 powered by a '93 VW VR6 Turbo GT3582R
    Go-karted Aug 5, 2016 - Then May 19+21, 2017
    Tracked May 27/July 26, 2017
    Build time before being driveable on Sep 27, 2019: over 6000h
    Build Completed Winter 2021

  6. #46
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    Hi

    I just saw your switch back circuit and Im planning to build one, but theres a modification I would like to make. My LED have this built-in controller that when voltage is applied it has this flowing effect, I tried to connect it to my flasher lights but I encounter this problem - it is not syncing.

    So I came up with this idea to hook it up to a constant 12v but the problem is it stays ON. I came up to your design and it looks the perfect circuit for my project but your circuit turns OFF the constant 12v when the flasher is ON.

    Heres what Im planning to change:
    1. Once the flasher turns on the circuit will be activated and it will turn on the LED supplying it constant 12v and vise versa.
    2. I will replace the NPN transistor with PNP (TIP107 transistor)
    3. Move R3 to the ground.

    Heres the circuit diagram
    Switchback circuit mod.jpg

    Please let me know what your thoughts. Im just new to electronics, Im consulting to avoid blowing up something

    Thank you and looking to hear from you soon

    Aries

  7. #47

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    If I understand, you need to apply steady 12V to your lamp module whenever the turn signal is on = flashing. When the turn signal is not on you want 12V turned off. Use this circuit for such function:


  8. #48
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    Thanks so much

  9. #49
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    Quote Originally Posted by aquillen View Post
    If I understand, you need to apply steady 12V to your lamp module whenever the turn signal is on = flashing. When the turn signal is not on you want 12V turned off. Use this circuit for such function:

    HI me again. I just realise we cannot apply the MOSFET switch in the Negative (-) of the circuit, because it is also connected to the white DRL, which means if the yellow is OFF, the white is also cause the negative is cut by the MOSFET. So I made this circuit, please let me know if this is correct, instead I will use a P channel MOSFET and put it in the constant positive (+) 12V.

    rev circuit.jpg

  10. #50
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    Quote Originally Posted by arieshton View Post
    HI me again. I just realise we cannot apply the MOSFET switch in the Negative (-) of the circuit, because it is also connected to the white DRL, which means if the yellow is OFF, the white is also cause the negative is cut by the MOSFET. So I made this circuit, please let me know if this is correct, instead I will use a P channel MOSFET and put it in the constant positive (+) 12V.

    rev circuit.jpg
    Can we use a relay instead of MOSFET?

  11. #51
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    This is so far beyond my ability to comprehend, my head is spinning. I read the entire post. You electrical guys are amazing! Thank you for the info, even tho I cannot take advantage of it. Isn't it great that we all have different fields of expertise?
    Thank you Aquillen, Frank818, and Frank c5r. Your intelligence is exceeded only by your generosity.

  12. #52

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    Lance it is just what a person learns, thankfully we all learn different things. Sharing is the key to a wonderful world.

    About the relay - yes a relay can be inserted, but you need that mosfet transistor because the gate on it does not consume current. We want a transistor that does NOT use current to switch on or off (mosfets transistors are voltage controlled whereas bipolar or "regular transistors" do use current).

    The two resistors and capacitor form a timer circuit so that that the circuit quickly switches state when the turn signal comes on, but holds it's state for a couple seconds after turn signal is turned off (that way blinking state of turn signal does not fool the circuit into changing state until the turn signal is really done blinking - i.e. completely off).

    The mosfet transistor (BS170 or IRF20, etc.) being voltage controlled, does not interfere with the current charging and discharging the capacitor. So the time constant of the R-C (resistor - capacitor) circuit is not modified by the transistor. A relay by itself won't work. You could fiddle with a diode charging a capacitor and turning on a relay with discharge characteristics setup by the capacitor value and relay coil resistance. But you would have a relatively high initial charge current to get the relay on, you need a pretty good size capacitor microfarad wise to keep it on between flash pulses, etc. If you change the relay for any reason and it is a little different coil resistance, your setup changes. So pain in the butt to setup.

    The mosfet is a tough transistor these days, I've used them for many years now in small to complex circuits and up to about 2000 ampere control setups. The only rule is to avoid exceeding voltage spec's on them and of course max current rating. This circuit is smaller than a relay and should work for most people.

    Use this circuit to control a relay directly if you need double pole contacts like a relay can give you. Add protection diode across the relay coil to protect the mosfet.

  13. #53
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    Quote Originally Posted by aquillen View Post
    Lance it is just what a person learns, thankfully we all learn different things. Sharing is the key to a wonderful world.

    About the relay - yes a relay can be inserted, but you need that mosfet transistor because the gate on it does not consume current. We want a transistor that does NOT use current to switch on or off (mosfets transistors are voltage controlled whereas bipolar or "regular transistors" do use current).

    The two resistors and capacitor form a timer circuit so that that the circuit quickly switches state when the turn signal comes on, but holds it's state for a couple seconds after turn signal is turned off (that way blinking state of turn signal does not fool the circuit into changing state until the turn signal is really done blinking - i.e. completely off).

    The mosfet transistor (BS170 or IRF20, etc.) being voltage controlled, does not interfere with the current charging and discharging the capacitor. So the time constant of the R-C (resistor - capacitor) circuit is not modified by the transistor. A relay by itself won't work. You could fiddle with a diode charging a capacitor and turning on a relay with discharge characteristics setup by the capacitor value and relay coil resistance. But you would have a relatively high initial charge current to get the relay on, you need a pretty good size capacitor microfarad wise to keep it on between flash pulses, etc. If you change the relay for any reason and it is a little different coil resistance, your setup changes. So pain in the butt to setup.

    The mosfet is a tough transistor these days, I've used them for many years now in small to complex circuits and up to about 2000 ampere control setups. The only rule is to avoid exceeding voltage spec's on them and of course max current rating. This circuit is smaller than a relay and should work for most people.

    Use this circuit to control a relay directly if you need double pole contacts like a relay can give you. Add protection diode across the relay coil to protect the mosfet.

    Thanks so much. Based on your comment I created this circuit. Did I got it right?

    circuit with relay.jpg

    Will this relay sufficient?
    Relay SPDT 10A .jpeg

  14. #54

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    Both should be fine.

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    Polarity Neutral?

    Quote Originally Posted by aquillen View Post
    PLEASE REVIEW POST 44 IN THIS THREAD IF YOU PLAN TO BUILD THIS YOURSELF FROM MY DRAWINGS.

    I build a lot of things instead of buying - within reason, and then sometimes without reason. I just like doing a lot of different things in a project. It's why I'm building an 818 - to do instead of buying "done".

    These days a lot of people who would never get into electronics, are doing so, with just a little info to get them going. This is not really a complex circuit by any means. If you have just a bit of skill, or an 'electronics type' friend who wants to help, or even a high-school kid who wants to learn and try it - I say go for it.

    I haven't done a PCB board for this yet but will, and will post up a drawing for that. It can be done just on a piece of perf board, etc. for that matter.

    I did the breadboard setup and tests, with several of the LED lights listed below, from Amazon. Also verified it works with the standard Subaru 3 terminal flasher module, with LED's. (in the olden days flasher modules often needed the "load" of incandescent lamps to do the flashing - hence I tested it). This would get in trouble running incandescent bulbs, or LED's drawing much over a total of 300mA (Q1 would get HOT at least if not fail).

    Other transistors (must be reasonably equivalent in characteristics to these) can be used, these are the ones I had in my junk boxes.



    How it works:

    With "turn signal off", Q2 is off, allowing Q1 to turn on. This lights the white LED's connected to Q1. When turn signal is energized, the Yellow LED's light by direct wiring through the flasher 12V. Also this turn signal 12V almost instantly charges capacitor C1 via diode D1 and low ohms resistor R1. The 12V at C1 and the gate of Q2 turns on Q2. Q2 turns off Q1 so the white LED's are turned off instantly.

    Once the turn signal is off, the high resistance in R2 begins to discharge C1. The resistance/capacitance time constant of R2, C1 takes about 2 seconds to discharge enough that Q2 can turn off. By this time a blinking turn signal has recharged C1 repeatedly so Q2 remains turned on. After the blink condition ends, C1 will finally be able to discharge until Q2 turns off, allowing Q1 to turn back on and resume the running white LED mode.

    With 6 each of some 50 milli-ampere white LED's connected to Q1 it can get slightly warm, so packaging of the circuit (pot in epoxy for example), should be such that it can dissipate some heat, about 1/4 to 1/2 watt is typical. Also the Q1 transistor case must be insulated from ground, etc.

    The LED's I tried were pointed out in another post here, I bought them and like them. Yes tiny wires, but that is all they need for the current demand in play.

    One way to package this might be in an Altoids box, or a cigar tube, then pot (filled) the container with some JB Weld. I believe JB Weld has metal filler but not to the point of being conductive enough to affect this circuit. The Q1 should be close to the surface of the container so it can pass heat out, but not touching. JB will move the heat out fairly well. If you get to fancy it finally reaches the point where buying a couple commercial modules would make more sense. But then you didn't build it yourself (818 wink).

    https://www.amazon.com/gp/product/B0...?ie=UTF8&psc=1

    If the link to the site goes bad, here is what they were described in the ad:

    Everbright 8-Pack White / Amber Switchback 12V 9W Eagle Eye Lamp Led Light Bulbs For Car Tail Car Motor Backup Light Fog Light Daytime Running Lights(DRL)

    This is exactly the type of circuit I'm seeking. However, being interested in old British sports cars, I have a requirement to make this work in both positive and negative ground cars. Having built the circuit with bridge rectifiers ahead of the switchback circuit, it fails to delay the return to marker, so the sequence is white-amber-white-amber instead of white-amber-amber-amber-white. Is it possible to make this in a polarity neutral version so that I don't have to make two different versions (I have several friends who want one as well, but there is a mix of positive and negative ground cars).
    Thanks,
    Lew Palmer

  16. #56
    Senior Member chmhasy's Avatar
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    For the people that don't want to deal with the chemicals and drilling of PCB's

    I have used the free version of eagle cad https://www.autodesk.com/products/eagle/overview design the pcbs and have used https://oshpark.com/ to produce some PCB's with great results.
    and the prices are very reasonable.

  17. Thanks aquillen thanked for this post
  18. #57

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    Quote Originally Posted by brittrix View Post
    Is it possible to make this in a polarity neutral version so that I don't have to make two different versions (I have several friends who want one as well, but there is a mix of positive and negative ground cars).
    Thanks,
    Lew Palmer
    Retracted my first reply after thinking instead of just writing. Also - would those pos gnd cars be 12V or 6V? Overall it would have to be redesigned though. I'll think about it and get back.
    Last edited by aquillen; 10-08-2019 at 12:51 PM.

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    Polarity Neutral?

    Quote Originally Posted by aquillen View Post
    Retracted my first reply after thinking instead of just writing. Also - would those pos gnd cars be 12V or 6V? Overall it would have to be redesigned though. I'll think about it and get back.
    All 12 volt.

    Thanks
    Lew

  20. #59

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    What vehicle is this?

  21. #60
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    Switchback

    Quote Originally Posted by aquillen View Post
    What vehicle is this?
    1950 MG TD and 1934 MG PA and 1936 MG PB

    Lew

  22. #61

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    Quote Originally Posted by brittrix View Post
    1950 MG TD and 1934 MG PA and 1936 MG PB

    Lew
    FYI looking into it. I'm assuming you would like to use the single cat eye style white/orange-yellow LED modules we started this thread for. Bit tricky working out a simple circuit for this because those modules are common cathode LED devices. Can be done but I'm trying to come up with minimal parts/simple circuit that is reliable of course. Let you know.

  23. #62

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    Lew, I haven't dreamed up a simple way to make a universal/polarity neutral circuit. Probably could with relays and transistors for example. With a lot of time spent I would probably get a hit, but after an hour or so I have one drawn using only transistors which should do specifically for positive ground. I need to test it and if good will post.

  24. #63
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    I appreciate anything you can offer, Art.

    Lew

  25. #64

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    We have gone somewhat off topic here doing positive ground designs. BUT, fyi I'm just waiting on a part I designed with this week so I can verify a circuit I want to post. Should have it next week and will update.

  26. #65

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    Switchback circuit for POSITIVE GROUND CARS (not 818's !!!)

    We are definitely off the 818 grid now for sure. I guess it was the challenge so here is a low cost solid state switchback circuit for positive grounds. It's so close to a universal circuit I should spend more time and get it there but... I leave you to layout the circuit board since I don't need one of these... I benched it but did not test with temperature extremes or way low voltage, etc. It works fine on my bench on 12V to 14V, should be good in a typical car.



    How it works:

    The dual cat-eye LED's are going to usually be common cathode which makes switching the anode sides of the LED pair a requirement. This addresses that problem with about as few components (low cost to boot) that I could think of. Setting up a time delay also makes using a normal coil based relay an extra complexity. Using a solid state opto-coupled mosfet switch (literally a solid state relay) helps simplify the timer circuit.

    With normal "lights on" battery negative power via R1 biases transistor Q1 to turn on which then powers the white LED.

    When the turn signal/flasher is on, battery negative is to be applied to both diode D1 and R2. Resistor R2 biases transistor Q2 to turn on and this powers the yellow LED at each flash pulse. D1 feeds the negative to the opto-isolator switch device IC1. Current flows through IC1 and R3 to the battery positive. Internally IC1 has an LED that sends light into an MOSFET switch that essentially functions as a relay contact. When the LED is on, the switch is closed. The closed switch in IC1 "shorts" the Q1 emitter-base so that Q1 turns off and the white LED is now off.

    During the signal/flasher on time, D1 also supplies charging current to timing capacitor C1 (this current is limited by resistor R4 to prevent excessive current in the diode D1). When the flasher goes into "off" time, C1 discharges slowly through the IC1 and resistor R3 path. C1 and R3 create a time constant so that current flows through IC1 for about 1-2 seconds and keeps IC1 "turned on". This keeps Q1 turned off during the off part of flashing, but only as long as the flashing continues so that C1 can keep getting charged.

    When flashing is off for a couple seconds or more, C1 finally discharges enough that IC1 is no longer kept turned on. Switch IC1 is off and Q1 again turns on lighting the white LED. A nice feature of this particular IC device is it has built in logic so that it switches off suddenly instead of fading from on to off as the C1 current supply "fades away", this means the white LED comes on suddenly instead of fading from off to on.

    IC1's pins 3 and 4 are interchangeable - when laying out a PCB you could swap them to simply the board layout if desired.

    If a separate connection to the cathode of the LED's from IGNITION on, etc., is a problem, then use a pair of diodes, one from the lights on and the other from blink on, to supply the BAT(-) to the common cathode of the LED module.

    enjoy!
    Last edited by aquillen; 11-03-2019 at 03:12 PM.

  27. #66
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    Is there any chance you have a gerber file to share? I'd consider getting a sheet made and make the boards available at cost. I tried my hand at CAD PCB design and just about lost my mind. I've made a dual channel version deadbug style in a small enclosure that works fine.. I would like to add a pair of active reflectors to the front and rear of my Honda Goldwing. Making single circuits wrapped in heat shrink would work much better than what I have right now.

    qsl.net/k2mpw/honda/gl1800 is my personal farkle page for the Goldwing.

    Thanks
    Michael
    k2mpw at that Ya Who dot com site.

  28. #67

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    Post 20 has pcb board image you can copy and produce from (after you scale it properly). I use a program called Boardworks from over 20 years back. It produces screwed up gerber files - had a professional board shop try to use that data once and they probably cussed me the whole time. If I ever make something that I need a bunch of I'll have to break down and use something from modern ages I guess.

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