Flip Flop - LM555

MikeMl

Well-Known Member

Most Helpful Member

• Oct 26, 2010

• #21

kinarfi said:

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

Click to expand...

I did in the previous post. The .asc file I posted should run if you open it with LTSpice. Get mine running, and then change it to add more stuff.

ps, I just tried it, and it simulated fine...

 

Last edited: Oct 26, 2010

kinarfi

Well-Known Member

• Oct 26, 2010

• #22

Yes, your sim works fine, the place mine was failing was at the switch, after analyzing yours, I notice the pulses of the voltage source for the switch needs a negative value, after fixing that, mine works fine also. Would you please send your .Model PushButton SW() or switch (SW) model and what does .IC V(C) = 11 do?
Thanks for the help,
Kinarfi

 

MikeMl

Well-Known Member

Most Helpful Member

• Oct 26, 2010

• #23

The SW model is on the .asc file I posted (no other files are needed) . The LTSpice switch is open if the control voltage is negative, and is closed if the control voltage is positive.
The switch has a bunch of defaults, which are in the LTSpice help file; Ron = 1 Ohm, etc. The .MODEL statement would be more complicated if you want to override any of the defaults.

.IC V(C) = 11 sets the voltage at node C to 11V at the start of the simulation. Try it without, and you will see what it does.

 

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• switch.png

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Last edited: Oct 26, 2010

kinarfi

Well-Known Member

• Oct 26, 2010

• #24

Thanks, Much appreciated!! Here's what my final is, at the moment, I'm always changing things.
Kinarfi

 

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• Divide By Two.asc

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kinarfi

Well-Known Member

• Oct 27, 2010

• #25

Mike, after reading your last post, which didn't say what I wanted it to, I started digging and found that one of MY problems was syntax errors and that you were correct, of course, every thing I needed was in your .asc.
When I ran MY previous .asc, I would get first attachment, then the second, and after my learning and correcting, my .asc runs like it should and I can change values around to see what happens.Thanks again for help.
Kinarfi

 

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Last edited: Oct 27, 2010

kinarfi

Well-Known Member

• Oct 29, 2010

• #26

kinarfi said:

Thanks, Much appreciated!! Here's what my final is, at the moment, I'm always changing things.
Kinarfi

Click to expand...

This design works great on the bench with FETs driving ≈ 2 amp lights, driven by a Lamda power supply, but in the vehicle, it tends to lock up and not switch, likes to to stay on high beam which pulls ≈10 amps.
It's a great circuit, one I've wanted for a long time, but for my camper, I have gone with this design, sweet and simple.
Thanks for the help,
Kinarfi

 

Attachments

• 47502d1288157050-flip-flop-lm555-divide-two.png

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• Camper Dimmer Swith.PNG

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J

Jaguarjoe

Member

• Oct 29, 2010

• #27

Your MOSFETs are good for 5 amps Id max. Your low beams draw 6 amps and your brights need 10. Something's gotta give.
Vgs max is 12v but they're running at 14.4. Something's gotta give.

There is no protection from 14.4v bus transients.

I know its not as much fun, but if you ended up with a maintained contact switch, why didn't you just go with a $5 automotive 30/20 amp SPDT relay that is bulletproof and proven to last? Or one of these with the original push button plan but more expensive:

**broken link removed**

 

Last edited: Oct 29, 2010

kinarfi

Well-Known Member

• Oct 29, 2010

• #28

OOPs, when I simmed this, the sim didn't have a IRF4905 55V-74A FET so I used the first International Rectifier on the list. I mounted them on a nice heat sink out of a computer server power supply, and I had the FETs on hand and they only cost $1.58 each. Don't expect any problems from them.
One question though, for every body, why does the IRF4905 come in a seal envelope with a humidity indicator and that moisture absorbing gel and baking instructions? Am I supposed to remove them periodically and bake them.
Kinarfi

 

Last edited: Oct 29, 2010

kinarfi

Well-Known Member

• Dec 20, 2010

• #29

Next time some idgit asks if a 555 will work as flip flop, tell him to just go buy a d flip flop for 30 cents and to not worry about it. That's what I should have done.
Kinarfi

 

Last edited: Dec 20, 2010