0-12v in 6 seconds

[FireAce]

Hey fellows, I need some help designing a circuit. Its kind of unusual, but being an N scale train modeler, I always need unusual circuits.

I have a "Diesel Engine" sound circuit I built that generates train engine sound depending on track voltage. Works fine, but I dont have an "engine start" sound.

I found if I slowly increase the power to this circuit, from 0v to its full 12v using a pot, it sounds like the engine and generator winding up. BUT, I would like to have it do this automatically when I hit the "Engine Start" switch on the control board.

A TIP31c comes to mind, as I found its output is sensitive to whats applied to the gate.

Any ideas?

 

[MikeMl]

How much current is drawn during the ramp?

What is the raw input voltage? (Head room question: after the ramp is over, what should the difference between the raw input voltage and the track voltage be?)

 

[FireAce]

Hey Mike, the creator of this circuit did not specify current draw. Here is the circuit, I built #3.

Diesle Sound

Basically it's 3 IC chips and an eight inch speaker. I have access to 12v or 15v DC power on my table. My thought is using the TIP31C. This would require using the 15v, so that with a resistor at the gate, I would still be able to receive 12v to the circuit. I figure a capacitor from gate to ground would control the time frame in which the engine would then "fire up"

 

[MikeMl]

Maybe I misunderstood? Isn't the ramp running the locomotive as well as making the sound? Put it another way, whatever voltage appears across the tracks, runs the locomotive motor and the audio card at the same time? If so, the current is primarily determined by how much the locomotive motor draws.

 

[FireAce]

Oh no Mike, not at all. The track voltage is determined by a motor speed control circuit. This feed ALSO goes to the engine sound module, but only to ramp it according to voltage in tracks.

The sound module has its own power source of 12v. The feed from the tracks is a secondary power for determining the ramp. With 0v at track, the sound module is idling, like a train engine at standstill.


Edit: I think I got it. 15v to TIP31C. Emitter powers sound circuit. 10k res from 15v to gate of transistor,(transistor output is 12v) with a nice fat cap sitting between gate and ground. Sounds exactly like a train engine coming to life, with the generator winding up and all.

 

[KeepItSimpleStupid]

Mike's good at this, but I'll drop a few crumbs: This is an integrator: **broken link removed** Bad choice because of the necessity to use negative supplies.

Probably a linear ramp isn't needed, so just "amplify the voltage across an RC" circuit rather than drive by a constant current source.

4 W is about 1/3 of an amp, so circuit would probably need to supply 0.5A.

Just bouncing ideas. Mike's good at this.

 

[MikeMl]

Ok, then who controls the ramp to the tracks (and the locomotive speed)? It is the guy controlling the throttle, right?

Do you want to replace the manual throttle with an automatic ramp circuit? In that case the ramp circuit has to power the tracks instead of the throttle, which means the ramp has to deliver an Amp or two.

The sound just follows the track voltage; you said it yourself. It makes no sense to have a ramp only on the sound if the ramp voltage to the sound generator bears no relationship to the actual track voltage.

 

[FireAce]

Mike, the confusion is this. The 0-12v I was referring to in my first post, was referring to the sound module power supply. Its actual power source. Not the ramping input.

And yes, the guy who runs the throttle controls the track voltage. This feed also goes to the sound module (once its running) and generates the sound according to speed.

 

[MikeMl]

So where does the six seconds come from? It seems like if you want realistic acceleration of the locomotive, where the sound follows the instantaneous track voltage, you have to slowly advance the throttle over a six second time. Isn't that just wiring the track voltage to the sound module? I am not getting what it is you want to build?

 

[FireAce]

Mike, your totally missing it. The throttling is taken care of. It worked fine before I started this discussion. This discussion is not about the throttling and ramping. Lets step back

There are two voltage sources going to sound module. The first one is the power supply. The second one is the track voltage for throttling.

Forget about track voltage. This is the confusion, I never was talking about that. The ONLY thing this discussion pertains to, is the power supply to feed power to the sound module.

In turning on the sound module, one hears a pop on the speaker, and all of a sudden you hear this train engine running. Well thats not realistic. This discussion is about taking the power source that goes to sound module, and instead of turning it on suddenly, it feeds it slowly, from 0 to 12v, over a period of about 6 seconds. This makes it sound like the generator is winding up from a dead stop.

That was the other confusing part. When I said "engine start", I wasnt referring to engine moving forward. I was referring to engine starting up first thing in the morning. The pistons are stopped. The pumps are off. Then we start the engine as you hear them start on Youtube. But as you prob read, I already got this using a TIP31C.

 

[crutschow]

I'm still slightly confused. How is the sound module turned on for the engine start? Is there a remote control for that?