Flip Flop - LM555

[kinarfi]

I need a divide by 2 flip flip, does the 555 work as a divide by 2 flip flop or do I need to just go buy a couple of them. Got several 555s.
Thank,
Kinarfi

 

[MikeMl]

At what frequency?
Over what range does the frequency shift?

 

[Jaguarjoe]

I haven't seen every 555 circuit but I have not seen a flip flop scheme yet.
If worse comes to worse, you can always use a 4013.

 

[kinarfi]

At what frequency?
Over what range does the frequency shift?

Once every minute or so. It's purpose is to act as a toggle switch, but the input is a momentary. Since everyone here likes details, my motor home has the old style foot operated dimmer switch and with my fused left ankle, I can't operate the dimmer switch, I plan to mount a N. O. push button switch, probably a tactile switch, on the end of the blinker and use the flip flop to activate either one of two FETs or Relays to power the head lights.
Kinarfi

 

[MrAl]

Hello,

If you have a set input frequency you can set the 555 up as a monostable and use it to divide the input frequency by a given number like 2, 3, 4, etc. The input has to be a constant frequency however because you set the 555 up with a certain timing that has to be related to the input frequency. This means if the input frequency can vary too much then it wont work.

 

[MikeMl]

Ok, so you are not doing "frequency division" and the periods between the switch operation will be irregular. Here is something that should work:

 

[MrAl]

Ok, so you are not doing "frequency division" and the periods between the switch operation will be irregular. Here is something that should work:

Hi Mike,

Yes, it does sound like this application is not a frequency division type problem. My mistake

 

[KMoffett]

Here is a 555 toggle circuit that I've built, that I think should be credited to Bill Marsden.

Ken

 

[MikeMl]

I took the circuit posted above, and sim'ed it in LTSpice. As drawn, it could have a problem with a bouncy switch. I changed the time constant of the low-pass filter section to make it more immune to switch bounce.

Compared to the circuit I posted above, this one has the advantage that you can use a spst momentary push switch. It's disadvantage is that it does not have complementary outputs, so you will have add more stuff if don't want to use a SPDT relay to switch between high and low beams.

 

[kinarfi]

I love this forum, Thanks for the help, I built and tested and will finish installing tomorrow, probably should have taken a picture. I've wanted this circuit for years and have tried designing it several times and several ways, but this one works. One neat thing about it is that every time you turn on your lights, it starts out on low beam, regardless of where it was when you turned it off.
Thanks all!!
Kinarfi

 

[Jaguarjoe]

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.

 

[kinarfi]

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.

Why did you toggle the low beams? -- The original set up is that way with a mechanical switch which give one or the other only. Also, and I've never tried running both beams in the same bulb for very long, it seems to me that having both elements burning at the same time, you would have a melt down. Have you run your head lights with both elements on and did it perform alright for you?
You may be correct, I didn't check the voltage rating on the 555, and since it's driving FETs, I can reduce the voltage to 10 or 11 and stabilize it there with an LM317. I took the motor home for a short drive and it didn't always switch, not sure if it's my button, the power, the design, or the voltage, plus, I still had the problem of the lights turning on and off by themselves, but at least the head lights did stay on, most of the time. Must have a problem with light switch itself. Still working on it.

Mike, I don't know spice well enough to do anything with what you sent me, but thanks.
Kinarfi

 

[MikeMl]

Here is the LTSpice sim file.

 

[KMoffett]

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.

Ken

 

[Jaguarjoe]

My Jag has 4 E-code headlights. 2 are dual filament HI/LO, the other 2 are HI only. When I switch the HI beams on, all 6 filaments are lit up. Looks like aircraft landing lights.
My F150 has dual headlights which I suspect toggle HI or LO. Here is something gets around that:

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National Semiconductor makes automotive voltage regulators like LM2930. Unfortuneately its only a 5 volt part. If you use the LM317, it will need some protection too like reverse input polarity and short circuit protection.

I forgot- make sure the 555 and other parts will work properly in the temperature environment they'll be in.

 

[kinarfi]

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;
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

 

[kinarfi]

Here is the LTSpice sim file.

Mike,
I must have burned up my NE555 spice model , I can't get my sim to work, I couldn't get my switch to work either, so I made a FET do the job. Most of my wave forms resemble yours, but the out won't toggle. I did manage to get your sim to NOT work by changing some to match mine(555Toggle 2.asc). Hope you still enjoy teaching, I need some teaching. Would you mind helping, Please?
What is the data for your switch?
Thanks,
Kinarfi

 

[MikeMl]

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.

 

[Jaguarjoe]

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 Jag's been that way for 11 years, still on the same lamps. I'm pretty sure they're 100W/80W units. Googling around, it looks like there is a multitude of headlight scofflaws out there.

 

[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.

Can you send me the model or what ever I need to make my sw work, I matched yours as exactly as I could, but couldn't get the switching action.
Thanks
Kinarfi