| Electronics > Beginners |
| issues install flashing module a car 3rd brake light |
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| SparkyFX:
--- Quote from: wojtek077 on July 03, 2019, 07:44:52 am --- --- Quote from: SparkyFX on July 02, 2019, 05:35:58 am ---The output to the third brake light might be PWM controlled anyway. --- End quote --- Yeah it might be, I just don't have a oscilloscope to test it. --- End quote --- Check the voltage with a multimeter while on, it gives you a different mean value when it´s not DC. |
| wojtek077:
--- Quote from: forrestc on July 04, 2019, 08:01:12 am ---My suggestion was to draw around 25W on the brake light circuit to force the voltage when off to drop to zero. i.e. put a 6ohm resistor in parallel with the entire thing. If the existing one is only drawing 1W this would be too much. You could also try a 3.3V zener backwards so that it adds 3.3V of drop. --- End quote --- Sorry late reply but what zener would use I'm getting overwhelmed with data sheets and how would wire it up towards the ground or positive side. --- Quote ---Edit/Addition: It also occured to me just after I posted this reply that there are circuits out there which will cut off below a certain voltage. Usually they're used to prevent overdischarging a rechargeable battery or prevent something from running at too low of a voltage. If you google 'low voltage cut off circuit' or 'low voltage disconnect circuit' you'll probably find a few. --- End quote --- I been looking but I couldn't find one. I found relay ones but I don't trust those. I wonder if there will be a delay with the zener? |
| wojtek077:
Something like this |
| forrestc:
See section 3 about a voltage shifter at this page: https://circuitdigest.com/tutorial/zener-diode-types-applications-and-operational-principle The resistor probably isn't needed in your application since your device will stand in as the resistor. You choose the zener based on the amount of voltage drop you need. You'll also need to size it big enough current-wise and power-rating wise so that the amount of current you're passing through the zener doesn't result in the zener overheating. |
| ledtester:
fwiw, here is, I believe, the first patent granted for a flashing brake light: #3,460,089 granted in 1969: https://patentimages.storage.googleapis.com/62/e6/3a/432bbdfbb55446/US3460089.pdf It is interesting to read how it works. No 555 timers or even any solid state electronics here: --- Quote ---When wire 12 warms, it expands permitting bus bar 5 to shift to the left under the expansive force of leaf spring 16 against stop 17, causing contact 6 to open. Without current coursing through it, wire 12 cools, contracts and closes contact 6 once more. In that manner the cycle is repeated. The frequency of the cycle can be adjusted by varying the value of the resistance in wires 11, 12, 13, the thickness of leaf spring 16, and the deformation of leaf spring 6 from its unstrained configuration. --- End quote --- |
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