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At what frequency?
Over what range does the frequency shift?
Ok, so you are not doing "frequency division" and the periods between the switch operation will be irregular. Here is something that should work:
Automotive electrical systems are notorious for spikes, dips and load dumps. I would be very leery of running the 555 directly from that electrical system. Max Vcc for the 555 is 16 volts and you're already at 14.x. It won't take a very large upset to kill it.
Why did you toggle the low beams? When my low beams are on they stay on even when the brights are on. I need all the light I can get.
I think a lot of headlights are high "or" low beam. On the ones I own, if the stick on the column is pushed forward from center it latches from low to high. But, if you pull it back from center (momentary switch), you can see that it lights both low and high beams together.Why did you toggle the low beams? When my low beams are on they stay on even when the brights are on. I need all the light I can get.
I have always assumed that running both elements would destroy the bulb, but wasn't sure, so I asked the manufacturer, here's their response;Why did you toggle the low beams? When my low beams are on they stay on even when the brights are on. I need all the light I can get.
Here is the LTSpice sim file.
I have always assumed that running both elements would destroy the bulb, but wasn't sure, so I asked the manufacturer, here's their response;
Hello Kinarfi,
Thank you for your inquiry. Halogen headlamps are not designed to support the heat generated by continuous dual filament operation and will fail prematurely. The heat generated by dual filament operation can also damage the lamp wiring harness and lens reflector assembly.
Also, it is illegal to energize both the low beam and high beam filaments simultaneously for an extended period of time. This method of operation is specifically prohibited under federal motor vehicle rules of operation. (Reference; FMVSS 108 ). The rules do allow for a momentary overlap to prevent a 'dark out' period when switching from low beam to high beam and back.
The following paragraph was copied from FMVSS108:
S5.5 Special wiring requirements.
S.5.5.1 Each vehicle shall have a means of switching between lower and upper beams that conforms to SAE Recommended Practice J564a Headlamp Beam Switching, April 1964 or to SAE Recommended Practice J565b, Semi- Automatic Headlamp Beam Switching Devices, February 1969. Except as provided in S5.5.8, the lower and upper beams shall not be energized simultaneously except momentarily for temporary signaling purposes or during switching between beams.
Sincerely,
Jordan Brown
Consumer Care Specialist
OSRAM SYLVANIA, Inc.
Kinarfi
The reason your version of the circuit doesn't work is because the "MOSFET switch" is not symmetric like a toggle switch. Remember that a MOSFET has a parasitic diode from drain to source which is always conducting in one direction.