"My guess is that they are shy to do it because of the litigious nature of the other 3-rail manufacturers."
And, if true, they aren't going to tell one of us that 
. Just continue to keep their head down and nose clean.
Maybe they sell enough and have their hands full supporting the product in its current form. They seem to be pretty successful with it. They've posted a few YT shorts with 3 rail engines so they're not totally ignoring 3 railers, they just don't seem fully engaged with 3 rail users. Maybe all the huff 'n puff smokey puff guys are are keeping them at bay. I dunno.
@Norm Charbonneau posted:It would be interesting to know some more info. What engine was this in? Any idea on the motor, gear ratio, etc.?
It's probably somewhat of a moot point what the motor, gear ratio, etc. is I would think. Just by it's nature, back-EMF cruise is totally incapable of keeping perfect sync with external wheel motion. It's analog nature gives it no way to synchronize exactly to the mechanical motion, some slippage is inevitable. Trying to have perfect sync with internally generated sound using back-EMF would be a fool's errand over any length of time.
That's not to denigrate back-EMF cruise, it's a very capable system, just not suited for exact mechanical synchronization. I'm perfectly happy with the cruise performance of boards using back-EMF, that would be a different topic.
@Norm Charbonneau posted:It would be interesting to know some more info. What engine was this in? Any idea on the motor, gear ratio, etc.?
I was light on the details because they were neither O gauge, and it was strictly speaking that chuff wasn’t synchronized with steam. I was getting NO chuff, yet the BEMF system WAS able to control velocity. So my circumstances were off-topic but the experience wasn’t. Both were on 3 rail British OO chassis I regauged for American OO. One was an older DC motor and the other was an open frame AC motor that I used the bridge rectifier trick to provide DC polarity based direction control.
I understand that both of these circumstances are way out on the bell curve of likelihood, complicated and those things tend to muddy up forum discussions.
I’ll end up using the Blunami I purchased for something else I’m sure (and if I could download alternative sound sets to it it would already be in a Diesel or electric engine), but I was super excited to use it. While I GREATLY prefer physical controllers, being able to read and see CVs via BT on a large touchscreen makes DCC livable. Would have been really handy for the DC/DCC circuits in my little 3-rail world.
@christie posted:I was light on the details because they were neither O gauge, and it was strictly speaking that chuff wasn’t synchronized with steam. I was getting NO chuff, yet the BEMF system WAS able to control velocity. So my circumstances were off-topic but the experience wasn’t. Both were on 3 rail British OO chassis I regauged for American OO. One was an older DC motor and the other was an open frame AC motor that I used the bridge rectifier trick to provide DC polarity based direction control.
I understand that both of these circumstances are way out on the bell curve of likelihood, complicated and those things tend to muddy up forum discussions.
I’ll end up using the Blunami I purchased for something else I’m sure (and if I could download alternative sound sets to it it would already be in a Diesel or electric engine), but I was super excited to use it. While I GREATLY prefer physical controllers, being able to read and see CVs via BT on a large touchscreen makes DCC livable. Would have been really handy for the DC/DCC circuits in my little 3-rail world.
Just about all of my steam projects will have Pittman 5 pole permag motors with ~18-20:1 gear ratios and very little backlash. These modern drivelines have very good electrical and mechanical resolution so Blunami plays very nicely with them. I deal with closed loop control for many types of systems in my day job and understand the need for good system resolution before any system of control is applied to it. Backlash, friction, mechanical slop and low resolution control will limit what tuning can dial in. 3 rail trains are in the outlier category for closed loop control using incremental encoder feedback and I tend to feel they are generally tuned a little too hot by their makers. Without the ability to tune to your liking you're stuck with someone else's idea of good energy management. BEMF is pretty much standard in the more popular scales and I think it's a better system overall especially with all the adjustment Blunami offers.
@christie posted:I was light on the details because they were neither O gauge, and it was strictly speaking that chuff wasn’t synchronized with steam. I was getting NO chuff, yet the BEMF system WAS able to control velocity. So my circumstances were off-topic but the experience wasn’t. Both were on 3 rail British OO chassis I regauged for American OO. One was an older DC motor and the other was an open frame AC motor that I used the bridge rectifier trick to provide DC polarity based direction control.
I understand that both of these circumstances are way out on the bell curve of likelihood, complicated and those things tend to muddy up forum discussions.
I’ll end up using the Blunami I purchased for something else I’m sure (and if I could download alternative sound sets to it it would already be in a Diesel or electric engine), but I was super excited to use it. While I GREATLY prefer physical controllers, being able to read and see CVs via BT on a large touchscreen makes DCC livable. Would have been really handy for the DC/DCC circuits in my little 3-rail world.
Back EMF motor control will not work on open frame motors.
Their motor control algorithms, whether strictly bemf pulse, or a combo of pulse and level, or whatever DID control the rectifier wired open frame ac motor.
It’s the chuff triggering that failed to work.
@christie posted:Their motor control algorithms, whether strictly bemf pulse, or a combo of pulse and level, or whatever DID control the rectifier wired open frame ac motor.
It’s the chuff triggering that failed to work.
Let me restate... It will move, but it likely won't be able to detect the field magnet pulses very well.
I'm guessing it uses some count of pulses to with a divider to trigger the chuff. If it can't reliably count pulses, if probably won't ever trigger.
@rplst8 posted:Let me restate... It will move, but it likely won't be able to detect the field magnet pulses very well.
I'm guessing it uses some count of pulses to with a divider to trigger the chuff. If it can't reliably count pulses, if probably won't ever trigger.
Back-EMF doesn't count field magnet pulses at any kind of speed, it just reads the back-EMF voltage when the motor drive is off between PWM drive pulses. I know that ERR does actually read the commutator transitions at very low speeds. However, once the motor is spinning at any speed, it's just reading the analog back-EMF voltage from the motor(s). You can't read anything back when the PWM output is driving the motor, so it's not possible to never miss pulses, even if you were trying to read them. Next, consider an 18:1 gear ratio, a typical value. Think about how many armature pulses there would be at any speed with a 5-pole or 7-pole motor.
I would expect that the Blunami is simply estimating the speed from the value of the back-EMF and using that to generate the chuff pulses.
I did the DDE (dynamic digital exhaust) procedure which I think is supposed to help Blunami characterize the motor response for steam exhaust sounds. I feel the chuff is pretty stable across the speed range I normally use but doesn’t seem right at really high speeds that I normally wouldn’t approach. I have yet to look into it more. I still believe most 3 rail trains have unnecessarily tall gear ratios for unrealistically high speeds.
In any case, sine John is now convinced that BEMF is unsuitable for chuff generation, he has made the case for a chuff input and not an output. That would allow for my dream of crankpin synched chuff and keeping smoke unit control external.
I will still say these Blunamis run amazingly well and have better running behavior than anything 3 rail command systems have attempted. The sound options are amazing and the lack of a chuff input is a bit of a wash right now since you don’t have to mess around with a chuff switch setup and it can save another evening or two when doing an install.
I have only installed a Blunami in one steam engine, an MTH Hudson. I get a pretty consistent 4 chuffs per rev as well. I only had to adjust the rate CV a few integers to get it close. The engine has a 94xx Pittman. Back EMF is OK though maybe not as good as ERR, still close enough. I have no complaints in that compartment. Only with not being able to sync the smoke fan.
Pete
@gunrunnerjohn posted:Back-EMF doesn't count field magnet pulses at any kind of speed, it just reads the back-EMF voltage when the motor drive is off between PWM drive pulses. I know that ERR does actually read the commutator transitions at very low speeds. However, once the motor is spinning at any speed, it's just reading the analog back-EMF voltage from the motor(s). You can't read anything back when the PWM output is driving the motor, so it's not possible to never miss pulses, even if you were trying to read them. Next, consider an 18:1 gear ratio, a typical value. Think about how many armature pulses there would be at any speed with a 5-pole or 7-pole motor.
I would expect that the Blunami is simply estimating the speed from the value of the back-EMF and using that to generate the chuff pulses.
I don't know what the gear ratio has to do with measuring back EMF.
I've seen systems that can measure the RPM of a motor, assuming you know the number of poles and program that into the calculation. I apologize for assuming that something that sophisticated was used in model trains. Though I don't know if we know for sure what SoundTraxx is doing on their boards, but given how good that people claim the chuff sync is, maybe they are doing something a little more advanced than ERR boards.
I haven't bothered to check but maybe there is a DSP on their Blunami boards to measure the ripple from the poles passing the magnets.
@rplst8 posted:I don't know what the gear ratio has to do with measuring back EMF.
Not much at all, that was my point. However, it does figure into when the smoke chuff is generated since that is directly linked to the mechanical motion of the drive train.
@rplst8 posted:I've seen systems that can measure the RPM of a motor, assuming you know the number of poles and program that into the calculation. I apologize for assuming that something that sophisticated was used in model trains. Though I don't know if we know for sure what SoundTraxx is doing on their boards, but given how good that people claim the chuff sync is, maybe they are doing something a little more advanced than ERR boards.
I haven't bothered to check but maybe there is a DSP on their Blunami boards to measure the ripple from the poles passing the magnets.
It would be knocking on the door to impossible to actually count the poles at higher motor speeds. For one thing, the poles would be going by faster than the width of the PWM pulses that are powering the motors, that along negates any ability to count those pulses.
We can debate this all day, but my opinion is that there's no way they accurately track the exact RPM of the motor over all speed ranges. That's what is necessary to synchronize the chuff with the external smoke unit chuffing. More correctly, no cost effective way that would be suitable for model train budgets. 
Guys you are going back and forth on an issue that doesn’t exist, at least with modern can motors used in O scale these days. I don’t know how they do it but it just works.
Pete
@Norton posted:Guys you are going back and forth on an issue that doesn’t exist, at least with modern can motors used in O scale these days. I don’t know how they do it but it just works.
Pete
Well, it does exist in the environment we're specifically talking about. That is the synchronization of back-EMF cruise with the external mechanical motion. I know how they do back-EMF, it's actually a fairly simple process.
