After several months of intermittent effort, I'm releasing my guide to designing/specifying the AC to DC converter needed to run the Blunami command controller card in locomotives using 3-rail AC track power. You will find it attached. While it is oriented toward 3-rail O gauge, the principles discussed are equally applicable to 2-rail S gauge. I hope to do an S conversion before the year is gone.
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Document updated to revision 1, which expands the section on twin can motors to include a third configuration option and implements various minor text and formatting edits.
Nice work @KarlDL. With the Blunami board being so small and thin, adding this setup should be easy even in some of the smaller engines.
Thanks for doing the hard part.
Ron
Thanks for doing the work and putting this together Karl.
I'm getting closer to the edge of the cliff.......
Bob
Can anyone recommend an inexpensive prebuilt ac-dc converter that doesn’t require additional components the dc-dc boards need, for use with the Blunami boards?
Has anyone converted a K-line Plymouth to Blunami using track ac while keeping smoke? Looks like the 2200 will easily fit but ac to dc conversion may be the issue.
@Trainmstr posted:Can anyone recommend an inexpensive prebuilt ac-dc converter that doesn’t require additional components the dc-dc boards need, for use with the Blunami boards?
Has anyone converted a K-line Plymouth to Blunami using track ac while keeping smoke? Looks like the 2200 will easily fit but ac to dc conversion may be the issue.
I plan on doing mine but with only a full wave bridge and cap. It will work OK just not give perfect speed regulation if track voltage changes. I am more concerned with finding a speaker that fits. Likely won’t get to that project until Fall.
Pete
@Trainmstr posted:Can anyone recommend an inexpensive prebuilt ac-dc converter that doesn’t require additional components the dc-dc boards need, for use with the Blunami boards?
Has anyone converted a K-line Plymouth to Blunami using track ac while keeping smoke? Looks like the 2200 will easily fit but ac to dc conversion may be the issue.
I did a reasonably thorough search and have not found any suitable, off-the-shelf, AC>DC converter/regulator that's configured for 18VAC input and suitable for O gauge motors. Lots of stuff available for 120VAC input. I did find an inexpensive AC>DC converter based on the LM2596N chip, but it's limited to 1A, so it's only suitable for lower-current S gauge engines (and that's if it will fit the loco). I would much rather have found an integrated solution and not spent considerable time figuring out the capacitor sizing formula and other details in my guide document, but couldn't find one. Nor has anyone else described any integrated solution in posts on the OGR Forum going back to last fall.
I have been using the AC/DC regulated converter shown in the attached photo of a BlueRail equipped twin can motor OGauge GP-30.
@BOB WALKER posted:I have been using the AC/DC regulated converter shown in the attached photo of a BlueRail equipped twin can motor OGauge GP-30.
MTH??? I have a PRR GP-30 with full PS-1 that I may (or may not) convert to Blunami, but two other locos are ahead of it in the conversion queue.
@Norton posted:I plan on doing mine but with only a full wave bridge and cap. It will work OK just not give perfect speed regulation if track voltage changes. I am more concerned with finding a speaker that fits. Likely won’t get to that project until Fall.
Pete
You can get away without using the DC>DC converter/regulator if the normal track voltage is at or below 15-16VAC, as the probability of exceeding the 26VDC supply limit of the Blunami card under surge/spike conditions is significantly less than that at 18-19VAC. Add a transient protection diode pair rated at 25V peak for additional security, at the rectifier input. I haven't explored the speakers used in HO engines, but there seems to be quite a bit of creativity in that arena and those solutions could work in the tighter S and O gauge situations.
Regarding the limitations of a bridge, this is true Karl and I am aware of that. I haven’t opened the Plymouth up yet so not sure how much room there is to play with or what motor current draw is.
Pete
Another source for voltage regulators is pololu.com. Click on their regulator link.
One that might work in a Plymouth is rated for 50VDC in max, 12v DC out, 2-3 amps and about 3/4” square. Of course you would have to add a rectifier bridge to the input.
More expensive than what is found on ebay and Amazon but its the first I have come across that might fit.
Pete
@Norton posted:Regarding the limitations of a bridge, this is true Karl and I am aware of that. I haven’t opened the Plymouth up yet so not sure how much room there is to play with or what motor current draw is.
Pete
Pete, the current draw of the Plymouth is minimal, the tiny motor won't tax almost any supply. I imagine a supply way small will do the trick for the Plymouth.
I use this small switching board for a power supply that delivers several hundred milliamps, surely enough to power the Plymouth. Add a bridge rectifier and a 470uf cap and you're in business.
This board is 22mm x 17mm, and about 1/4" thick, It's rated at 2A, but I don't count on them for more than around 300ma.
@gunrunnerjohn posted:Pete, the current draw of the Plymouth is minimal, the tiny motor won't tax almost any supply. I imagine a supply way small will do the trick for the Plymouth.
I use this small switching board for a power supply that delivers several hundred milliamps, surely enough to power the Plymouth. Add a bridge rectifier and a 470uf cap and you're in business.
This board is 22mm x 17mm, and about 1/4" thick, It's rated at 2A, but I don't count on them for more than around 300ma.
I did find another on on the bay that has specs similar to the one at Pololu. 12v out at 3 amps peak, 2 amps continuous for two bucks. Slightly bigger than Pololu’s about the size of the one you suggested. The Blunami is a two amp board so I would like to provide at least that much. Blunami ratings include all current demands including lights and sound besides motor drive.
Pete
Pete, take that 2A with a grain of salt, the one I pictured claims 3A, but at around 600-700ma, it's starting to get pretty warm. I did actually get 2A out of it with a DC bench supply as it's input, but it was running around 90C, way warmer than I'd be comfortable with.
Also note, you'll need some pretty large capacitors on the input to get 2 amps out of the switcher.
I count on 300ma or so with my little supply.
For two bucks I will take a chance. I can always use them for other stuff but I don’t expect to try them out for another few months.
Pete
If they ever release the Android version, I'll give one of their decoders a try.
The inductor seems to get the hottest on the ones I have.
@gunrunnerjohn posted:If they ever release the Android version, I'll give one of their decoders a try.
It's already on the play store, works great so far! Been using it for about a week now on this little guy:
Maybe I'll see if the Blunami will fit in the Plymouth switcher. 
Want to put one in my porter, if I could ever figure out how it comes apart!
I’d like to try my hand at a Blunami conversion. I’m not an electronics guy but have converted a MTH Premier PS1 Blue Comet to PS2 using their kit. I have a Williams scale 44 Ton I want to convert. Can anyone please recommend a bridge rectifier, capacitor, and dc-dc buck to complete this task? If all goes well I’d like to add electric couplers, I’m assuming either MTH or Lionel has something that’ll fit. Want to build this as a surprise for my grandson who likes running this engine and loves coupling and uncoupling cars. As a five year old he prefers using the phone apps or LionChief controller so Blunami fits right in.
Another question, since he uses Fastrack exclusively should I add some type of capacitor to the Blunami to negate continuity issues? He gets frustrated with running the engine conventionally at slow speed cause it sometimes goes into neutral (yes I clean his track and check the pins).
@Darrell posted:Want to put one in my porter, if I could ever figure out how it comes apart!
The Porter is a PITA to take apart!
@gunrunnerjohn posted:The Porter is a PITA to take apart!
Still want to do it!
@Trainmstr posted:I’d like to try my hand at a Blunami conversion. I’m not an electronics guy but have converted a MTH Premier PS1 Blue Comet to PS2 using their kit. I have a Williams scale 44 Ton I want to convert. Can anyone please recommend a bridge rectifier, capacitor, and dc-dc buck to complete this task? If all goes well I’d like to add electric couplers, I’m assuming either MTH or Lionel has something that’ll fit. Want to build this as a surprise for my grandson who likes running this engine and loves coupling and uncoupling cars. As a five year old he prefers using the phone apps or LionChief controller so Blunami fits right in.
Another question, since he uses Fastrack exclusively should I add some type of capacitor to the Blunami to negate continuity issues? He gets frustrated with running the engine conventionally at slow speed cause it sometimes goes into neutral (yes I clean his track and check the pins).
Not knowing the space inside the 44-tonner model, it's difficult to know if and how the cards will fit. Any FWB rectifier rated at 100PIV, 8A or higher will do, as will a 680uF 35V electrolytic capacitor, in this case. Here's the link to the converter/regulator I'm using with twin can motor diesels: https://envistiamall.com/produ...er-supply-module-usa. You can also find it on Amazon.
As for the track power interruption matter, the specified capacitor provides a slight bit of storage to bridge short gaps. The difficulty of bridging longer ones in a loco, as compared to a lighted car, is the far higher current draw of the motor(s). I haven't had any problems on GG/Ross track and have no experience with FasTrack.
A bridge rectifier followed by the capacitor mentioned n the previous post will convert the track AC to DC and provide some protection against momentary track power dropouts. I would also add a 12 or 15V fixed regulator as a protection against accidental overvoltage applied to the Blunami module. Ron045 has done this upgrade on the 44Toner successfully and you might want to check his comments.
You will have no problem fitting it all in the Williams 44-ton engine. I put a ERR Cruise Commander Lite and the ERR Railsounds Commander in one. Given the two tiny motors in the engine, the Blunami 2200 should do the trick, it's tiny compared to the ERR stuff. You'll have tons of room for the AC->DC power supply.
@Norton posted:I did find another on on the bay that has specs similar to the one at Pololu. 12v out at 3 amps peak, 2 amps continuous for two bucks. Slightly bigger than Pololu’s about the size of the one you suggested. The Blunami is a two amp board so I would like to provide at least that much. Blunami ratings include all current demands including lights and sound besides motor drive.
Pete
Pete, I picked up a couple of these. I got the 12V model. 2A continuous is a pipe dream! I tested it at 24 to 26VDC input with an 8 ohm load, that's 1.5A output. The regulator chip got over 100C in a couple minutes and I shut it down. However, with a continuous load of 12 ohms for a 1.0A output, it topped out in the high 70's, so I'd rate it as a 1.0 amp continuous supply. However, I figure 1A with peaks up to maybe 2A at times is doable with the board. I'm guessing another limit will be the size of the input cap after the bridge, I'm thinking on the order of 2200uf after the bridge. Most of these little boards don't react well to too much ripple in the DC input.
@gunrunnerjohn posted:Pete, I picked up a couple of these. I got the 12V model. 2A continuous is a pipe dream! I tested it at 24 to 26VDC input with an 8 ohm load, that's 1.5A output. The regulator chip got over 100C in a couple minutes and I shut it down. However, with a continuous load of 12 ohms for a 1.0A output, it topped out in the high 70's, so I'd rate it as a 1.0 amp continuous supply. However, I figure 1A with peaks up to maybe 2A at times is doable with the board. I'm guessing another limit will be the size of the input cap after the bridge, I'm thinking on the order of 2200uf after the bridge. Most of these little boards don't react well to too much ripple in the DC input.
Got mine last week but just tested them now. I agree they are duds. The one I tested just had no regulation when attaching a load. No load 12v and change out. 7 ohm load and it dropped to 7 volts out. They should be OK for LED lighting strips but definitely not Blunamis.
Pete
WOW, yours are not as good as mine. Mine worked at 2 amps, but it was hotter than a pistol. It'll probably work for my Plymouth switcher, the stall current of the motor is around 1/4A.
@gunrunnerjohn posted:WOW, yours are not as good as mine. Mine worked at 2 amps, but it was hotter than a pistol. It'll probably work for my Plymouth switcher, the stall current of the motor is around 1/4A.
Now there's a term I've not heard in a long, long time!
Revision 2 of my AC track power interfacing guide can be found at the beginning of this thread.
Can you share what you did for the electrocoupler interface board? I was thinking of something like that for my first Blunami conversion.
GRJ, check your e-mail!
@Norton posted:Another source for voltage regulators is pololu.com. Click on their regulator link.
One that might work in a Plymouth is rated for 50VDC in max, 12v DC out, 2-3 amps and about 3/4” square. Of course you would have to add a rectifier bridge to the input.
More expensive than what is found on ebay and Amazon but its the first I have come across that might fit.
Pete
Norton, Again your recommendation put me to the place I wanted to find. Pololu regulators look to be my answer for a regulator in the small space available. I ordered one rated for 12v, 2.8a, I fed the 18.5v ac into the rectifier, cap and then to the regulator. I hooked this up to the track and ran an American Models GP pulling 15 cars for 30 minutes. The temp on the regulator after that amount of time was 105 degrees F, very acceptable temperature for inside the locomotive.
The small size of this regulator will make for easier installation of Blunami decoders in S gauge locos, thank you.
Ray
I've found these to be useful, from Amazon, 2 ampt to peak 3 amps.
I'm sure there are others out there but I got thes 6 for 2$ each...
@Rayin"S" posted:Norton, Again your recommendation put me to the place I wanted to find. Pololu regulators look to be my answer for a regulator in the small space available. I ordered one rated for 12v, 2.8a, I fed the 18.5v ac into the rectifier, cap and then to the regulator. I hooked this up to the track and ran an American Models GP pulling 15 cars for 30 minutes. The temp on the regulator after that amount of time was 105 degrees F, very acceptable temperature for inside the locomotive.
The small size of this regulator will make for easier installation of Blunami decoders in S gauge locos, thank you.
Ray
Ray, I only bench tested them with a 5.5 ohm load and agree, temperature rise is not a concern. I haven’t gotten around to installing them yet.
Also good to know about the 4-5 amp alternatives.
Pete
@MR_P posted:I've found these to be useful, from Amazon, 2 ampt to peak 3 amps.
I'm sure there are others out there but I got thes 6 for 2$ each...
These buck converters are to large for the limited space in most S gauge American Models diesels as are most buck converters, they may be useful in American Flyer or in steam engine conversions as you can see below.
Ray
You really need to take some of the current ratings of these modules with a grain of salt.
@MR_P posted:I've found these to be useful, from Amazon, 2 ampt to peak 3 amps.
I'm sure there are others out there but I got thes 6 for 2$ each...
I have these in stock, and they do better than some, but at a 2A draw at 9V, they're already at 165F on the regulator, going to 15V out at 1.7A and the regulator is now at 180F, hotter than I want things running inside my engines. I could only get 15V out from an 18V transformer, so that's as far as the testing went. I went back and checked and the regulator temperature is still rising, it's at 190F now.
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