Electronic background help needed with circuit

[ger_uk]

I'm in the process of my install and I'm using a creative zen as my mp3 player. I've soldered two wires on the Zen's on/off switch, but to turn it on and off they need to make contact for 2-3 seconds.

I've been playing around with 555 timers, capacitors and relays with no luck now for about a week, but I'm no electronic engineer. This is what i need

turn on ignition
>relay triggered for 3 seconds then off

turn off ignition
>relay triggered for 3 seconds then off

If theres anyone out there with an electronic background who can help, all i need is a diagram, i can do the rest.

I'd really appreciate it...

Thanks, Ger

[czechplastik]

I suggest you make contact with stef or bog, they'll soon sort you out

[Bog]

Thanks for for the recommendation CP , but I'm not that good with electonic circuits - basic circuits and electrics I'm fine with, but what what is a bit beyond.

Ger, I think Stef is you best bet! Like you I know the basics, know what I want and how to achieve it (Sort of) and when I see a circuit, I can normally figure out how it works.

I assume you would have a circuit along the line of the one below which Stef designed for his Homing Lights project (Here: Install Homing Lights )

sc.jpg

I can see how his circuit holds the power on for 4-5 seconds, but how you would modify to hold the power when the ignition is turned off is a bit more complex.

As CP says, try a PM to Stef, he's very good at this sort of thing and is vey helpfull.

By the way, I'm curious, are hard wiring your ZEN into the car? Can you post some more details or pics - sounds very interesting

Let us know how you get on

[ger_uk]

Thanks Bog, I'll give Stef a pm later. It's been driving me mad, I've been using livewire circuit simulation, and done loads of circuits, but I'm stuck.

I bought a damaged Zen 60gb on eBay, the screen was damaged, but works using the av out connector. This is ideal for us guys, same interface as the ipod, but it's visible all the time. Looks really good on the nav screen. I want to hard wire everything in and make a Fiberglas mould for the controls.

This is only the front setup, I've installed two screens for the rear, and I'm ruining them off a hard drive media player, so the kids can use a remote to select what they want to watch. This is also connected to the front screen, which has 2 av inputs and the reversing camera, i did this by building using jupido's circuit.

Some pics below, will take so more soon, all i need now is the switching circuit and I'm ready to go.

[Koen]

I was more thinking about the follwing. Beware, it's just a quick drawing, not tested, no values for Rv and C.
How (I think) it works:
- When switching your civic on, there is a voltage at the accessory input, making the transistor switch.
- Current starts flowing through the relay making it switch on.
- Capacitor C starts charging through Rrel. (the resistance of the relay) + Rv.
- When the capacitor is charged, the current stops and the relay swiches off. Rv and C should be calculated/tested in such a way that the time constant (time to charge the capacitor) is 2 to 3 seconds.
- When turning your civic off, the transistor open gain, and the capacitor discharges trough the relay, making it switch again.

Remarks:
- There can be no protective diode over the relay, but the transistor is protected against inductive current by the diode over it.
- The relay cannot be "polarity-sensitive".
- Rv cannot be to big, since it woul reduce the current to much, and that may prevent the relay from closing.
- C must be rather big, because it needs to hold the power to switch the relay on again. (4700 µF, maybe more. 16v types are ok.)


Currently I do not have the time to build and test this, but you could give it a try.
If think 15 min longer, I might come up with something more clever. Unfortunately my time is limited...

K.

[ger_uk]

Cheers Koen, I'll give it a go in Livewire later and play around with it. I'll keep you updated. Thanks

[ger_uk]

Hi K, Been playing around, but with no luck I'm affraid... I cant get the simulation to work, tried loads of different values.

[Koen]

I'll check tonight if I 've got the necessary components, and I'll build it on an exp.board. Can't be to hard IMHO. I'll keep you posted.

K.

[spongeybob]

Hi Ger, Try this.

Been giving your little problem some thought. Haven’t tried it but I think it should work.
The circuit is based on a cheap comparator (LP311). When power is first applied the Opto-Coupled switch (FOD852) is switched on for approx 3 seconds (C1 charging via R2) when power is removed C1 is rapidly discharged via D1 and R1 switching the opto-coupler back on until C2 run’s out of charge.
I must stress that I haven’t tried it. It’s come straight out my head. Don’t blame me if you blow up your Zen!!!

[ger_uk]

Hi Spongeybob, Thanks for the help, only problem I've got is I'm using Livewire to simulate the circuits before i build them, but i cant find the comparator (LP311) in the components so i cant test it. Does it have another name by any chance?

Cheers

[spongeybob]

Hi Ger,
I chose the LP311 for it low power consumption, Try simulating using a LM111, 211, or 311

[ger_uk]

thanks, will have a go this evening, have to go out and do some x-mas shopping today... just had a quick look, i have the lm311, but it has different pins (see pic)

What should i do...

Ta

[spongeybob]

Hi Ger,
Not familiar with ‘Livewire’ but it looks as though some of the pins on your LM311 have been removed for simplicity. A real LM311 must have pin 1 connected in order to work.

See http://cache.national.com/ds/LM/LM111.pdf

I have redrawn the circuit with the opto-coupler in a different position. You could substitute this for an LED to get your simulator working.

Have fun…

[ger_uk]

Did the circuit, still no luck, can't get it to work, i think i've followed your diagram correctly. see below.

[spongeybob]

Hi,
Does your software allow you to open and close the switch during the simulation?
If not, to simulate the opening and closing of the switch you could try replacing SW1 and B1 with a pulse generator set to +12V 0.05Hz
As you can see from my simulation the output goes low when power is applied and removed.

[ger_uk]

Yer it does allow me to switch during simulation, i don't think my software likes the lm311. This is starting to do my head in now, really appreciate your help though

[spongeybob]

Glad to be of help. I know how you feel.

[Stef]

It is so simple that it hurts:

Check that the relay coil impedance is about 300ohm or more.
Check that the +12V after ignition that you use is not turned off when you press the start button.
If the circuit gets +12V after ignition the relay will be on for about 2 secs (higher cap= longer time).
If you turn off the ignition, this point becomes "virtual" ground and the relay will turn on again for about 2 secs.
Have fun!

[Stef]

Simulation of the circuit

[spongeybob]

Well done, I like it.