Adventures in TMCC & Legacy... Trying to master the 455Khz track signal. I've built the test car, and it is finally working..

cjack posted:

Anyway y'all had me confused.

The HF special in the 200uA DC-current mode has a 1k Ohm shunt or burden resistor.  With no change in the circuit, they can switch the meter to DC-voltage mode which measures the voltage across 51k Ohms.  Readings of 30-40 uAmps using the 200uA DC-current mode would instead be 1.5 - 2.0 Volts in the DC-voltage mode. 

The reality as I see it is simple.  It doesn't matter what units the meter is measuring (voltage, current, widgets, etc.); the readout gets larger and smaller proportional to the received 455 kHz signal.  And all this occurs over a wide range making it a useful and remarkably inexpensive tool.

Yes, if I were doing it I'd prefer the Voltage measurement mode...but I'm not doing it.  I'd say that ship has sailed and the standard has been set.

Matt Makens posted:

If it came out of the box it might be bad from that Genesis I had to upgrade. Try a different board 

Thanks Matt. That was in a bucket with your name on it. Not sure if I have another. We had ordered a couple of ERR's did they all get installed? I thought there was one for that Lakawanna switcher. You did the MTH TC&W, the MTH CP switcher. I thought there were 3. That board may be from the Genesis. I haven't got any spares that I know of. CRAP.

stan2004 posted:

cjack posted:

Anyway y'all had me confused.

Yes, if I were doing it I'd prefer the Voltage measurement mode...but I'm not doing it.  I'd say that ship has sailed and the standard has been set.

Alea iacta est, eh?

cjack posted:

Alea iacta est, eh?

Translation: "The train has left the station"

Test the board in an engine first, then install it in the car.  Making sure you have control of the light will insure the board is working in the test rig.

gunrunnerjohn posted:

Test the board in an engine first, then install it in the car.  Making sure you have control of the light will insure the board is working in the test rig.

Good point John, I'll have to open up an engine to do that. Not my favorite thing, but I can. I'll have to run down to the hobby store and grab the R2LC tomorrow. Project on hold for today, lots of other projects to work on.

Anything new Elliot?  .   Yes or no is good enough. 

Sorry to report Gregg nothing new on this yet. The one R2LC board that I had loose turned out to have been a dud. It had come out of an engine where the whole TMCC unit was replaced.Now I know the rest of that unit was probably OK and it was just the R2LC.

I'm reluctant to grab one out of a good engine, so the plan is to hit the LHS. Unfortunately, the one guy who has access to the parts is only there for a short time on the weekends. I stopped by last Saturday, but my timing was off by a few hours, too early.

The store is about a 20 mile schlep, and I don't like making special trips if I can help it. I have two more shots this weekend, as I have other train activities both days and can just pop in on my way past. If that fails, I'll just order a few online. Seems like a good part to have spares.

This is still a very important project, and needs to get done, but I can be patient about it. There are plenty of other things to do while I wait.

I'll let everyone know when the party starts.

Elliot, what are you going to do with that R2LC dud?  Are these routinely repaired, saved for scavenger parts, or just tossed?  If the latter, would you send it to me? 

I don't run TMCC and don't plan to but this signal-measurement discussion has been going on for years and I'm curious. I suppose I could get lucky and repair the board using schematics I see on the web...in which case I can mess with the signal-measurement pin13 circuit and Harbor Freight meter using a 455 kHz signal generator rather than a TMCC base.  Whether or not I get it running I'd return it - your worst case out-of-pocket would be ~$3 for USPS First Class package shipping.

Stan, in my world they're just tossed. They are machine made with all those tiny components. Even if I could figure out which one was bad, I probably couldn't fix it. I'd be willing to "donate its body to science". Shoot me an email, and I'll send you the carcass.

They are really fixable except for the programmed chip. You can replace drivers, caps, etc. and the rf chip. The SMD is doable for most folks.

Big_Boy_4005 posted:

Stan, in my world they're just tossed. They are machine made with all those tiny components. Even if I could figure out which one was bad, I probably couldn't fix it. I'd be willing to "donate its body to science". Shoot me an email, and I'll send you the carcass.

Email sent.  Check you junk email folder

cjack posted:

They are really fixable except for the programmed chip. You can replace drivers, caps, etc. and the rf chip. The SMD is doable for most folks.

Oh good, glass half full!  Earlier Elliot reported there was no voltage being supplied to the RF chip so I'm hoping it may be something simple in the power supply which I should be able to repair.  My interest is getting enough working to fiddle with the signal-strength part of the circuit.

Well gang, this project is back on!

I finally found a brave and helpful person at the hobby store, who was willing to risk death, and go back in the parts room and get me what I needed, a couple brand new R2LC's. Always good to have a spare. I should be back up to speed on this by mid week. I've been busy with other stuff while I was waiting.

Q: Does this thing need to be programmed for use in this project, or is it just good to go as is?

Stan, the bad one will be in the mail to you in the morning. I'll be interested in hearing what you find.

Given the radio signal for TMCC, is there a ideal recommended antennal length? 

BTW:  I'm making one of these nifty devices too.  Dunno why, since I haven't experienced any serious reception problem areas on my layout.  But just for fun I guess.

455khz?  Given the wavelength of the carrier is around 657 meters, the longer the better!

If you are talking about a signal testing car, my antenna is a horizontal brass rod 7" long.  I see saturated signals of 62 uA at some places, so this antenna may be on the "large" side.

I HAVE A WORKING TEST CAR!!!

I got the pin 13 lead soldered onto the chip of the new board. Makes a world of difference. The light even works. The meter is reading 36 to 41 on the short section of track I dragged it over. There's a slight problem with the chassis I used, as it is leaning slightly and is making intermittent contact with the ground. Physical problem, not electronic, should be a quick fix.

We're open for business!

Congratulations, Elliot--March is off to a good start!!!

Thanks Carl, but not so fast. I'm going to have to locate another chassis, because this one had the living crap run out of it back at enterTRAINment. The axel bearings are so worn that the side frames are dragging against the center rail extensions on every switch, in a glorious Fourth of July style display. Thank God I didn't fry the new board.