Hi everyone. This is my first post as I have just joined the society. I have purchased a 4 volt Japanese micro chassis and will be using a 12volt transformer. Looking for advice on what type of fuse I should install and how to install it. Please note I have very little space for the fuse.
I fitted a 100 ohm resistor in series with the motor. This worked fine from 12v. These chassis will run slowly the problem is electrical pickup as they are so light.
Hello Tony,
Firstly, welcome to the Society.
I've never read of anybody installing any kind of fuse protection in these circumstances, but perhaps it has been done. As Alec mentions, people tend to use a resistor in series, and various values have been mentioned in the past - anything between 50 and 470 ohms! Testing your loco by attaching the resistor between the controller and track feed so it is easily changeable (crocodile clips are your friend!) will allow you to determine what works best for your controller. Just take it easy as you do the trials and don't wack it up to fll power immediately or it will end in tears! WHen you have found a resistor that works for you, install it in the loco.
Julian
P.S. I should have added to look at this thread for a more informed discussion: https://www.009society.com/forum/index.php?topic=4066.0
Yep, all the experts have posted on that thread, no need to add any more here!
Just to add something that hasn't been mentioned on that other thread Tony, and this might depend on which of the Japanese chassis you have and what you intend to use it for, is that a lot of the 'electric mice', especially the Tsugawa range, use a lower voltage (3 or 4) 6 mm diameter motor. Sven at Tramfabrieik sells a 12 volt can motor that is also 6 mm diameter so it can be used to replace the low voltage one but is a little longer (4or 5 mm?).
I've just done such a conversion (to the Tsugawa chassis that will go under the new Narrow Planet 10hp Baguley loco). The easy bit is unsoldering the motor wires from the chassis so you can remove the original motor, just don't forget to make a note of which colour motor wire goes to which side. Slightly more involved is removing the worm from the shaft, but following a tip of using a pair of pliers to support the worm (between it and the motor body) and a broken drill bit (less than the shaft's 0.8mm diameter) to gently tap the shaft through the worm I not only got the worm off to fit onto the 12v motor (Sven's small motors also have a 0.8mm shaft) but I also have the original 3 or 4v motor to use on something else (like some lineside animation?).
Quote from: Tony Clark on May 24, 2020, 00:41
Looking for advice on what type of fuse I should install and how to install it.
A fuse is an electrical safety device that operates to provide overcurrent protection. So it won't do diddly to to protect your motor from over voltage until too much current flows, which may well be too late for your motor.
With a 12V supply you need to drop about 8V. So a resistor about twice the value of the resistance of the motor - in series with the motor should do the trick. But like Julian says trial and error to determine the 'best' value may be solution. Start High and sneak down.
HTH
Andy
I see Tony's logic in asking about fuses. It it excess current more than voltage that is likely to harm the motor. It is the current that heats the windings.
It is probably impractical to put current limiting in an 009 loco itself, but having current limiting in a controller is more realistic and hopefully all commercial controllers have some form of limiting, though it is quite probably set to a generic value appropriate to a particular gauge or range of gauges. I'm not aware of any that offer variable current limiting that could be adjusted to suit the occasion.
Adjustable current setting is something often found on bench power supplies and it is a relatively straightforward circuit for an electronics hobbyist to make. Some designs even have 'foldback' whereby once the maximum current is exceeded it drops until reset rather than being held at the permissible maximum, and so behaves a bit like a fuse. The problem of course is remembering to set the current limit for each locomotive when in use!
When Graham Farish was at Poole they supplied an electronic component that they called 'The Gizmo' which they recommended to protect their loco motors from over-current. It is basically a self-resetting 300mA current limiter which is more than enough current for an N gauge or 009 motor. As mentioned above it is usually too high a current that burns-out motors rather than voltage.
The resettable fuse is wired in series with the layout's 12v controller input and it then protects the whole layout. Such components are available from: https://uk.rs-online.com/web/p/resettable-wire-ended-fuses/5176613/ (https://uk.rs-online.com/web/p/resettable-wire-ended-fuses/5176613/). They're so cheap you could buy a few and experiment to find the 'trip current' rating that best suits your locos. They don't call them 'Gizmos' these days although I quite liked that name!