Print

Please login or register.
1 Hour 1 Day 1 Week 1 Month Forever
Login with username, password and session length.

[Peter Binns]

Has anyone tried to install a Model Radio Workshop sound generator in line with with an Mtroniks ESC and found that the ESC fails to respond or behaves erratically? The supplier of the sound generator suggested that the 1.2A BEC output from the Mtroniks ESC was too low to power both it and the sound module and recommended replacing the ESC with one from Hobbywings, fit a separate battery to power the RX, or install a separate BEC.


Reluctant to ditch the usually trusty Mtroniks ESC and having no room for another battery pack I tried a Foxy Pelikan UBEC but it still made the ESC behave erratically, stopping and starting independent of the throttle position. I then tried a simple buck converter between the main 12v lead acid battery and the RX stepping down the voltage to 5v but it didn't work at all. Maybe a dodgy connection or at only 1A output, just too little to do anything.


Model Radio Workshop have been very helpful in suggesting possible causes eg long speaker wires causing radio interference, but I wondered if anyone out there had ever had a similar experience and how they resolved it.


Many thanks.

[malcolmfrary]

https://modelradioworkshop.co.uk/shop/specialised-items/model-boat-sound-generator-steam/


The instructions indicate that it drives a loudspeaker of not less than 8 ohms directly.  It is also indicated that it does this off the receiver power line.  Off 5 volts, it will try to pull almost 2 amps at full volume.  That would be pushing 10 watts, which would be a huge speaker in a boat.  It is also much more than the BEC in the ESC can provide.  Depending on the other loads on the supply, it might be more than the UBEC can give, depending on the model chosen.  I didn't see anything about tweaking the volume in the instructions.
Running the unit off its own supply, having disconnected the ESC red servo lead, should leave the ESC nice and stable running on its own BEC.  But if the load of the radio, any servos and whatever else is plugged in exceeds the UBEC rating, that voltage will become unstable.  Generating stable control pulses (the receivers job) depends on it having a stable voltage to work on. 

[Peter Binns]

Hi Malcolm


That's very helpful, thank you. The speaker I am using is 10W nominal 8ohms. I wanted good volume! As you say, this is probably drawing too much juice. I don't think the volume is adjustable (anyway, reducing it would defeat the object).


So, to be clear, what I can try is:
a) Keep the sound generator in line between the ESC and Ch1 of the receiver but cut the red (and the black?) wires from the ESC so that the signal wire still runs through the sound generator and on to the receiver to control the unit
b) Connect an independent power supply to the sound generator using the cut red and black wires. Question - for this could I use a buck converter to step down the voltage from the main 12v battery to 5v that delivers say 5A?


Your confirmation/correction of this would be much appreciated!


Thanks again.

[malcolmfrary]

Hi Malcolm


That's very helpful, thank you. The speaker I am using is 10W nominal 8ohms. I wanted good volume! As you say, this is probably drawing too much juice. I don't think the volume is adjustable (anyway, reducing it would defeat the object).


So, to be clear, what I can try is:
a) Keep the sound generator in line between the ESC and Ch1 of the receiver but cut the red (and the black?) wires from the ESC so that the signal wire still runs through the sound generator and on to the receiver to control the unit
b) Connect an independent power supply to the sound generator using the cut red and black wires. Question - for this could I use a buck converter to step down the voltage from the main 12v battery to 5v that delivers say 5A?


Your confirmation/correction of this would be much appreciated!


Thanks again.

a) (and the black?)       NO.  You need the black wire so that the signal wire has something to refer to.
Just looking at the pictures of the unit, for a fairly powerful amp, it seems to lack the usual electrolytic capacitors across its power supply.  These are usually there to reduce hum, but since this is essentially battery powered, that might not have been considered. 
b) Using a Buck Converter of appropriate power capability "should" be exactly the same as using a UBEC.  In this case, they are doing the same job.  It "should" provide  a smoothed output, it might need something extra.  With the ESC red lead disconnected, it will supply 5 volts to the sound unit and the rest of the system.  The rest of the system relies on a very steady voltage to provide the steady signals required for predictable operation.  Both the rest of the system and the sound unit offer a varying load, which the power supply has to cope with in providing the regulated voltage and the current required.


The wire needs to be disconnected because two regulated supplies might not be regulating at quite the same voltage.  They tend to fight it out, and there is a winner and a loser.

[Umi_Ryuzuki]

The simple way to test this, is to leave the ESC in the off postion, and attach a 4 cell  battery pack to power the receiver.