I have a Atlas Gold series engine with QSI sound that I'm trying to consist with another Atlas engine with a Digitrax non sound decoder. I can get the speed of these two engines fairly close and both engines run smoothly until you couple them together. Once coupled together they will run fine for a few feet and then they act like you've put on the brakes. They slow down, then speed back up, slow back down, and so on. Could this be a back efm issue? I have a engine with a Tsunami sound decoder I had speed issues with until I lowered the value of the cv for the back efm on it and once I did it consisted fine. I'd try this with the QSI sound engine but I can't seem to find the cv for the back efm for this engine. I need some direction if anyone has any ideas. Thanks.
Clay Smith
Hopkinsville Ky
to the forum.
On the QSI decoder there is a Regulated throttle control, Standard throttle control and Back EMF throttle. To change it to standard throttle is an indexed CV. Change CV49 to 4. This tells the decoder your going to change the way it controls the motor. Then set CV56 to 0. These changes will give you standard throttle like the non sound decoder.
Hope this is helpful.
Pete
I pray every day I break even, Cause I can really use the money!
I started with nothing and still have most of it left!
I consist my Atlas gold GP40's with the default regulated control and have no problems. As loco noted it might be the odd ball causing the issue. Try standard throttle control like he said. Usually regulated throttle control will run fine with others but the they may not be speed matched close enough and causing issues.
Springfield PA
Pete,
CV 49 was already at 4 but CV 56 was 113, so changed it to zero as you suggested. This appears to have solved 90plus% of the problem. Thanks so much!! These units power a detour train that only runs once a session and not every session so I can live with how they're running now. I have posted to 4 other forums, and tried Atlas but they wouldn't let me join, with no answer. I really appreciate your help.
Kindest regards,
Clay
Clay.
Your very welcome. QSI using indexed CVs for configuring locos is s challenge sometimes. You will find that once you set a CV it will change later on down the line. One CV will control several things the decoder does.
To get your locos to run together reliably you must at least speed match them together. A non sound loco will typically run faster then a sound loco. Slowing the non sound loco to match the sound loco is the best option. This can take anywhere from a few minutes to hours of changing CVs and experimenting. Changing CV2, 5, and 6 is a start. A lot of times you will have to add momentum also to get them to start together. Tweaking CVs 3 and 4 will help them run together also.
Sounds like the problem is both engines having some form of Back EMF. BEMF allows the engine to allow continually at the same speed, even when going uphill or downhill. Going uphill, the decoder draws more power for the motor, going downhill, it draws less.
The problem is when you are running two engines with BEMF together. Let's say the first one is a tiny bit faster than the second one. When the second one fells the first one tugging on it, it thinks it's gravity pulling it downhill, so it tries to slow down. The first one senses the increased drag and assumes it's going uphill, so it adds more power. Of course the second engine then tries to slow down even more. It's a vicious cycle.
You can adjust the BEMF in one engine to either turn it off, or perhaps just lower the threshold where it kicks in. Then they should run together fine, if they are otherwise set pretty close in speed to each other.