How can I activate turntable sounds?

I don't know if you'll consider this "simple", but here's a circuit I've used in several locomotives to energize the relay when the motor is running, sounds like what you're looking for.  This will energize for either direction, and you can adjust the capacitor at C2 for the debounce time delay.

$3.27 on eBay with free shipping from Asia:

http://www.ebay.com/itm/321476...e=STRK%3AMEBIDX%3AIT

You power the module with 12V DC (which you apparently have).  Put light on the sensor to trip the relay - note there's a sensitivity adjustment.

Any light bulb that puts out sufficient light at 1V would undoubtedly pop at 12V.  So you can replace the photosensor with GRJ's optoisolator input circuit to provide the sensor current into the relay module.  Or if you have a couple Infrared LEDs lying around you could hook them up back-to-back to create an "AC" light source; the key is IR LEDs work fine at 1V - other colors (red, green, white, etc. typically light up at 2-3V).  Still need a resistor as GRJ shows for case when 12V is applied.

If for whatever reason 1V is not enough to trip the circuit, you could add a pair of back-to-back diodes in series with your motor.  So the diodes would eat 0.7V going to the motor but you get an extra 0.7V (either polarity) to trip the sensor.  This would work with GRJ's circuit too; I notice he shows a min voltage of 1.2V - though I suspect 1V vs. 1.2V doesn't matter for what you're doing.

Way to think outside the box Stan, never thought of IR.

Thank you both.  Order the module and put my thinking cap on, which has a big hole in the "electronics knowledge" area ...

I ordered a couple of the modules Stan found, they look useful!

Received the light relay module.  Here's what I suggest you do.  Use back-to-back red LEDs with a 470 ohm resistor.  Aim the 2 Red LEDs at the photoresistor as shown. 

When the voltage reaches about 1.5-1.6V DC, the LED is bright enough to trip the sensor if the module (led current about 0.2 mA).  When the voltage is 12V DC, the LED is quite bright and of course still trips the sensor but the current into the LED is limited to a safe current (about 20 mA).  As shown, one of the LEDs is on.  If polarity is reversed, the other LED would turn on.

Since a 1.5V trip voltage is perhaps a bit above your requirement, you can add 2 back-to-back diodes so that there is more voltage at the light sensor circuit than at the turntable motor.  So the relay will trip when the trip when the turntable reaches about 1V.  I don't know how much current your turntable motor requires but I'd think generic 3 Amp diodes should be enough - maybe 25 cents each.

Notes.

1. You can use Infrared IR LEDs (instead of Red LEDs) which turn on at a slightly lower voltage.  It works but the photoresistor supplied by the eBay module is not very sensitive to IR energy.  I replaced the photoresistor with an IR phototransistor and it works great but obtaining IR LEDs and IR phototransistors can be a hassle in onesy-twosy quantities.

2. The relay module is meant to be one of those turn-on at night detectors.  So the relay actually trips when it is "dark".  This simply means you use the NC contact to supply power to your sound module.  The module draws about 1/2 Watt when the relay is closed so it's not a big deal that the relay is closed when sound is off.

3. The relay module requires a 12V DC power supply.

4. I don't know what you're using for a motor drive, but I'd think that is has some kind of 0 to 12V DC source... and the DC voltage goes to a DPDT switch to reverse polarity for motor direction.  If this is the case, then I'd think you could go inside the controller before this DPDT switch where the voltage is a single polarity.  If you can find this voltage, then you only need 1 Red LED and resistor.

5. The sensitivity adjustment on the relay module needs to be near the most sensitive setting (Clockwise) but not fully clockwise.

Thank you!!  Just what I needed.  I'm waiting on delivery of the relay.  Would it help to enclose the entire setup in a "black box", nice and dark?

Good point.  I forgot to mention that you need to put the LEDs and photoresistor in a dark enclosure!  As the one photo shows, the red LED is very dim at 1.5V but that's all it takes to trip the module when the sensitivity adjustment is set near the full CW position.

As a point of interest, the opto-isolator that GRJ used in his circuit does just that.  It is in effect two back-to-back LEDs in opposite polarity aimed across a small gap at a photodetector - all encapsulated in a "dark" package.  But it's no "fun" because you can't see what's going on! 

I assume you'll mess around with the parts on the bench if for no other reason than to experiment.  As shown, LEDs with the rounded-dome lens project the maximum light energy out the top, hence the two LEDs are at a diagonal to aim at the photo-resistor.  So as you adjust the orientation of the parts, you then need to turn off the room lights or cover it up to actually test it.

Sure Stan, but the "fun" is that it'll work in a lighted room!

Is there a good source for obtaining the photo activator LEDS, ones which will produce enough light at a low voltage to trigger the device?  What is the two-in-one LED?  Will it handle the reversal of the DC current to the motor?

The LTV-8141 that GRJ uses in his circuit should work.  65 cents at DigiKey...plus shipping.

http://www.digikey.com/product...-8141&vendor=160

You still need the resistor as GRJ shows.  There are 4-pins on the LTV-8141 (GRJ's diagram shows 6-pins but that is incorrect per the DigiKey datasheet link).  2-pins are inputs going to the back-to-back LEDs.  2-pins are outputs which would replace the photoresistor on the eBay unit.  The hookup would look something like this:

The LTV-8141 is a so-called AC optocoupler - it has 2 internal LEDs to handle either polarity of input.  You can also buy DC optocouplers which have only 1 internal LED but they require the correct DC polarity input to work.

If you go this route, the detector side of the optocoupler is implemented with a photo-transistor which is a semiconductor and hence has polarity.  It must be hooked up with the proper polarity so inquire again.  The eBay module as supplied uses a photo-resistor which does not have polarity and can be hooked up either way. 

I'm not at all electronically smart so hopefully I can figure this out.  I have the circuit board for the sound module which appears (from this diagram) to have a "trigger input" for an optical coupler setup.  Would what you are outlining here function in that capacity?  When I apply current to the turntable motor (DC current) this would make that optical coupler activate on the circuit board, regardless of which direction the turntable was going?  The lower right diagram?

Well, if your sound module has an optocoupler compatible input, you don't need the eBay optical relay module.  To handle bi-directional drive, you'll need to use an AC optocoupler like GRJ uses rather than a DC optocoupler as ITT shows in their diagram.

Note the numbers of the 4 pins on the optocoupler.  You'll see some kind of dot or indentation or whatever on the package indicating pin 1.  Based on their diagram the connections would be exactly as shown above. 

Stan, the diagram morphed from one that had a bridge rectifier and a DC opto, it had six pins.  I just hacked out the bridge and relabeled the opto, I didn't bother to draw a different picture.

I take it you couldn't afford the bridge toll...and with the toll booth in both directions to boot.

Less parts with the AC Opto, that was Jon Z.'s suggestion.

Wow, that sure became simple once "refined".  I just needed to ask the right guys!  On the side, it's taken 4 months of asking various places to come up with this approach.  You da best!  Thank you!

The resistor can go in either way, there is no polarity.

Is this the resistor which will work?  A 330 carbon film type?

That will work.  Be sure it is rated 1/2 Watt or more.

1 watt would be safe?  I'm looking at Stackpole's list ... The turntable power supply puts out up to 20v DC to run it.  What should the resistance rating be?

If you can get 20 volts on the TT motor, I'd bump that resistor up to around 470 ohms.

470ohms 1 watt?  I could order higher if necessary, they list a bunch.

I have the same TT Module and have been trying to come up with a better way to run it. I have Millhouse turntable and it operates fine at a range between 3 (crawling)and 6 volts which looks to be about right as far as top speed. I realize everyone's TT may not fall into this range. Presently I use a 5 volt relay to turn on the power required for the sound module. Works well except when you really make it crawl the relay starts to chatter. Usually less than 3v. I'm electronically challenged but I can follow instructions. If Stan's last pick is all I need to do. It looks like a good 1 night project that will probably take me 3.

 Not sure how this could be accomplished. The one negative to the sound board is the volume. It pretty much is a constant speed.When the bridge stops the sound cuts out non realistically. It would be nice if there was a way to make the volume fade out or up as the speed of the bridge changes. My other idea at one time was to use a TMCC driver and soundboard from a GG1. 

 You guys that provide this info. are fantastic to share your thoughts on these projects.

Yup, we have one smart group of 3Railers on here, that's for sure.  Lot smarter than I am on this stuff.  I couldn't point out an electron if it ran across my workbench, except I think some leaked out of my DDA40X ... it's lost it's mind again.

I was looking at the sound module website and if I understand it, the audio output power is "only" 1/2 Watt?  I realize with the proper speaker and such 1/2 Watt can sort of fill a room...but for simulating a turntable I'd think you'd want to feel the groaning and moaning of the mechanism? 

This goes to issue of volume.  There are audio amplifier ICs/chips/modules where volume is proportional to a voltage - a feature called "DC volume control" for obvious reasons.  I didn't find any low-cost (under $5) amplifier modules on eBay with this capability...so you might comment on how fat your wallet is.

I'm assuming you don't want some contraption where the volume control knob of some audio amplifier is somehow coupled to the speed-control shaft/knob of your turntable motor controller.

The THAT 2018C VCA looks like the elegant solution based on Stan's comments.  It would require some work, so it may not fit your plans.

Well, this is another textbook example of "nothing is so easy as..."

Identifying suitable component parts to do this is easy.  It's the design of the circuit and assembly that requires the mind's imagination to go into overdrive!  For example, if I were doing it I'd probably just use the audio amp taken from a surplus PS2-5V board. 

It has DC-volume-control and puts out 5 Watts as I'm imagining I'd want to crank up the 1/2 Watt output from the sound module.  The part is now obsolete but then again I'd only be building a one-off.  It would take a dozen or so other inexpensive components (resistors, capacitors) but a lot of soldering and experimentation.  I figure at one time there was an evaluation module made by the manufacturer with the TDA7056 and auxiliary components that would vastly simplify the job, but that time is history.  I found some new audio amp chips with DC-volume-control that have an evaluation module but they were very expensive (over $20) and of course would still require some fiddling to make them compatible with the signals and voltages in the turntable drive.

If anyone needs one or two of those TDA7056B amplifiers, I have them.

Let's assume you want to old the current to the 50ma max in the opto-coupler, maybe call it 40ma for a little headroom.

That would be 475 ohms at 3/4W at a maximum.  I'd probably want a 2W resistor for this task.  At around 2 volts across the motor, you'll have 2ma through the opto.

In looking at the whole circuit, I'd opt for a safety margin and probably go with a higher value resistor, it doesn't look like you need that much drive, consider something like a 680 ohm resistor.  A 1 watt 680 would do the trick.

Parts have arrived from Digikey ... now to try to set it up without burning anything up!