I saw a note somewhere on this site that LocoFi would not work with pulsating DC. I assume that means it will not work with an MRC Loco-Motion 1500 power pack, since it has a pulsating DC waveform for all settings other than 0% and 100%. At 0% the voltage ism zero, and at 100% the voltage is a virtually constant 18 to 19 Volts. But between 0% and 100% the waveform is a combination of a variable DC value and a ~ 18 volt pulse. See the attached waveform for the 50% power setting. 0 is in the middle of the screen.
The waveform file did not upload, and for some reason the forum will not allow me to upload the file.
You can see all three waveforms at this link, three as bmp files and one also as a PDF:
https://1drv.ms/u/s!AtJVKvMETvjfhqsk9NPRf80a8awRKw?e=7tmlIg
Locofi recommended using bridge rectifier https://www.amazon.com/gp/product/B08JM5XQQW/ref=ppx_yo_dt_b_asin_title_o08_s00?ie=UTF8&psc=1 and a capacitor https://www.amazon.com/gp/product/B07M8PJKGJ/ref=ppx_yo_dt_b_asin_title_o00_s00?ie=UTF8&psc=1 my Locofi equipped engine ran fine after i added these betreen my power source and the rails.
I’m confused. The MRC Loco-Motion produces pulsating DC. A bridge rectifier is designed to change AC into DC, but I have DC to start with.
The rectifier and capacitor could also be used as a filter to smooth out the pulsating DC, is hat what the purpose of the bridge is in this case? However, without a series resistor the capacitor is placed directly across the pulsating DC output of the Loco-Motion (well, with two diodes in series) which could, in time, damage the Loco-Motion.
I could cobble together a straight DC power supply, if that is what I need for the LocoFi.
If you keep your MRC Loco Motion at or near “full” all the time, then you may get away without a bridge rectifier and the filter cap. Please make sure that the peak voltage (if there’s any AC component present in the waveform) does not exceed 24V at any time.
The information regarding this can be found under FAQ -> Troubleshooting -> 02.
@x For the “pulsed” DC supplies that are always fluctuating between 0 and peak voltage (even with full throttle on the power pack), we recommend an additional bridge rectifier for two purposes:
1. If only filter cap was present and the “direction” was reversed on the power pack, the filter cap will blow up. Having a bridge rectifier ensures safety.
2. Usually “pulsed” power packs are 16VDC which means the peak voltage is a little over 25V. If it was filtered straight, it will exceed the specifications of the LocoFi™ module’s maximum input voltage. Adding the bridge rectifier drops the voltage by about 1.4V and makes it fall within specs.
Our promise is that if you have existing DC power supplies, they can be made to power your track for LocoFi™ equipped locos. However, we find that typical MRC type of power supplies is not only bulky but at most offer 1A of current. That is good enough to run 1-2 locos only.
Instead, if you had an old laptop power supply (free), it’s not only compact but provides “clean” DC and is usually capable of 4-5A of current output. Similar inexpensive power packs are now widely available. See for example, https://www.amazon.com/dp/B07GFFG1BQ that can be had for <$12 and will easily support 6-8 locos. You can even have several of them with common GND to power as many locos as you wish.
So if I were to use the laptop/led light style power supply in the amazon link above, since it has overload, over voltage, over temp, and short circuit protection, I could just connect it directly to the tracks, correct?
I have the MRC Tech II Rail Master 2400, and have watched your video ( https://www.youtube.com/watch?v=SBryDInEkqA&t=316s) where you use the 1000uF 50V capacitor across the constant 15vdc, and I could certainly do that, but it seems like that laptop/led supply is potentially less of a safely hazard then having the capacitor hanging out in the open like that.
I am going to be ordering my first locoFi module and I am really looking forward to giving it a try. I have been using a couple of Bachmann BlueRail locomotives and the consisting hasn’t been working too smoothly and it will be nice to have sound coming directly from the locomotive itself vs just on the phone.
Dan
So if I were to use the laptop/led light style power supply in the amazon link above, since it has overload, over voltage, over temp, and short circuit protection, I could just connect it directly to the tracks, correct?
Yes. Absolutely.
…but it seems like that laptop/led supply is potentially less of a safely hazard…
True. In fact, these laptop type power supplies are not only safe but compact, rated for high current and very cost effective.
I am going to be ordering my first locoFi module and I am really looking forward to giving it a try.
We guarantee that you won’t be disappointed.
it will be nice to have sound coming directly from the locomotive itself vs just on the phone.
This is one area where LocoFi™ has an edge. No other WiFi or Bluetooth based modules offer that without hooking up an intermediary DCC sound decoder.
