I'm trying to connect a spare remote start key fob to a cellular relay so I can start the car using an app on my phone. I have to lock and unlock working fine but I need something to produce two quick (~.2 second) pulses to activate the remote start feature. So, once power is applied to the circuit it should give two quick pulses mimicking pressing the fob button twice. I had this working on another vehicle using a FRM01 timer but the shortest pulse it can be set to is 1 second which is too slow for the new vehicle. Any advice would be great. Thanks

 

Welcome to AAC!
If you have circuit building and programming skills a small MCU would likely be the simplest solution. If not, a circuit based on a 556 (dual 555) IC would do the job.

 

Should probably go with 556 based circuit. I have some basic electronics skills but not much experience designing my own circuit. Do you have an example of something that would work?

 

Here's a sim of a basic design. You would need to use the CMOS version of a '556 to keep idle current down if the circuit is to be battery powered. Depending on what the circuit has to drive, the output might need a power transistor stage added. Note that the first pulse of the two is slightly longer than the second pulse.

 

Here's a sim of a basic design.

Don't see it.

 

Here is my offering, although more complex than Alex_t’s circuit (using three 555 timers and more components) it has more flexibility allowing independent setting of both pulse widths and the delay between the pulses.

All 3 ICs are 555 timers – IC1 is initiated by the supply switch on, the pulse high time is set by Rt1 and C1; with Rt1 = 18KΩ the first pulse width will be approximately 0.2s.

The output of IC1 triggers IC2, which gives the delay time between positive pulses. If Rt2 = 47KΩ, the delay between pulses will be around 0.5s.

The output of IC2 triggers IC3, giving the second pulse; again with Rt3 being 18KΩ, the second pulse width will be around 0.2s.

The two positive pulses from IC1 and IC3 are fed to the circuit output via diodes D3 and D4.

To avoid the possibility of IC2 & IC3 being triggered by supply switch on, a 0.1uF capacitor should be added between pin 5 and 0V of these two ICs.

 

Don't see it.

Simulation file attached.

 

what program do I use to open the simulation?

 

what program do I use to open the simulation?

LTspice.
Free download from Analog Devices.

 

Below is Alec's circuit slightly modify by biasing C6 so that the first pulse is essentially the same length as the second (if that's needed).
I also increased the value of C1, since the power-on trigger wasn't working in my simulation.

 

Here's crutschow version using TI TLC556 model converted to LTspice.

 

Thanks everyone, I should be able get this built.

 

using TI TLC556 model converted to LTspice

Can you post the TLC556 lib file?
Thanks.

 

Also take a look at the TimerBlox series of IC's.
Me and the 555 always had issues for monostables especially unwanted power-up pulses.

 

Also take a look at the TimerBlox series of IC's.
Me and the 555 always had issues for monostables especially unwanted power-up pulses.

My 555 timer cookbook gives advice on avoiding power up triggering of the IC; which is a common problem especially where the trigger input (pin 2) is capacitively coupled.

With a 0.1uF capacitor between pin 5 (control voltage) and 0V; this keeps the timer reset (during power up), as the input at pin 2 is then always higher than the voltage on the 1/3 Vcc at the internal comparator of the 555 timer.

 

Here was the deal. I purchased a cool timer kit for Audio back when there was FM and turntables and non-IR remotes.

So, the timer trigger was filtered audio (Station goes off the air) and could connect to the tape monitor loop or the speakers.

Two timing modes: 1) 10m to 2 hrs and 2) 0-20 min after audio stops (turntable, tape deck, FM station off the air)
Since the knob was concentric, you got 1 hr and 10 min for my standard settings.
This was 555 based.

FM, LP's and TAPES got signal processed and the sound was very good in my opinion. An FM MPX processor (The Carver TX1-11). TAPES were recorded in dbx (really high frequency response and dynamic range). The 4bx had "Impact restoration" which could make you hear the hammers attack the strings on a piano or hammer dulcimer.

Friends have upgraded the 5bx. That system is really rare and contains compression.

I use a sucky Noise canceling Bose Quiet Comfort II Headset. Early versions just break mechanically. It doesn't cancel low frequency Bass.

String and tin-cans probably sound better.

I've heard a surround sound system that I helped put together for a TV that sounded pretty good.

For now, "music" is just noise and it gets irritating. My elderly mom listens to an AM radio. I listen to sucky FM on a car radio and on the Internet on Shoutcast.com. Sound on a Cell phone is crap too. I can't achieve silence because of tinnitus and outside low frequency noise that I know isn't tinnitus.

Google can;t or won't normalize the youtube sound. Closed capioning won;t stay set. The Samsug TV app, won;t let you use a real keyboard to enter search terms. The arrow keys and return (Same sort of controls on the remote).

I watch less TV and listen to less radio now than I ever did.
Sorry for the long aside. Concepts have been debated endlessly.

I bought an audio signal processor, a dbx 4bx, which used two push buttons (OFF and On/Mute). If OFF, the first push on ON/Mute turned the unit on and muted. The second unmuted it. The interface was an Opto-FET and an LM334 current source. I also detected power up with an optocoupler.

With the 4bx, if you pulled the AC cord, it lost all of it' settings.

1st job, Pulse the OFF button when the timer went off. 2nd job, when the timer was turned on, pulse the ON button.
3rd mode - detect the change to ON of the 4bx and strobe the timer so the IR remote could turn on the system.
Power glitches still do to this day, turn the system on. Sometimes it's just the 4bx unit.

I used the LM3905 timers: http://www.farnell.com/datasheets/2173854.pdf?

Where the glitch is, I don't know.

There is basically an ON/Standby mode to turn the timer on. The power switch on the audio timer does turn the timer off and turning the timer off causes the 4bx to get it's OFF button pulsed with residual power available in the audio timer. No glitches if the power to the audio timer is OFF, I think. If it does glitch, you lots of loud audio.

I think the system only stayed on for the timing interval after a glitch. I don't really know. Maybe that explains the 4bx being on and the audio system being off.

Two many triggers, 1980's technology. NO IR control for anything except the 4bx. An added CD player, initially a portable one, had IR control.

The audio system has been in disrepair for a while. "Music" isn't music anymore. The car radio gets rid of the boredom, but eventually that may go away as technology "progresses". Smart TV sound is horrible. It strains the ears for some reason.

 

Can you post the TLC556 lib file?
Thanks.

Hi

Here is TCL555 model modified for LTspice.
Also contains TLC555 and TLC556 symbols and demo circuits.

eT

 

Hi

Here is TCL555 model modified for LTspice.
Also contains TLC555 and TLC556 symbols and demo circuits.

eT

Appreciate it.
Thanks.

 

I guess I need to ad the pot and potentiometer symbols to my installation of LTspice. I found a couple of files and tried adding to the sub and sym folders but I still get an error when opening 555 Gated Pulses.asc and 2-pulser.asc. does anyone hase these symbols and please explain how to add them to LTspice. Thanks

 

I guess I need to ad the pot and potentiometer symbols to my installation of LTspice. I found a couple of files and tried adding to the sub and sym folders but I still get an error when opening 555 Gated Pulses.asc and 2-pulser.asc. does anyone hase these symbols and please explain how to add them to LTspice. Thanks

post the files