Kiha 40 Build

[dmustu]

Hello All,

 

On a visit to Japan in 2017, I came back with a Neko Publishing Kiha 40 kit and chassis. Recently delivered was the lighting kit for it,  and since moving house mid last year, I now have the space to build it!

I also got some Kadee No. 5 couplers for it, rather than use the plastic couplers in the kit, and some seating to go in it, as the kit is not supplied with any interior detail. I wanted to use the interior from a Kato oha 12, but couldn't find any so got a Tomix ohafu 50 interior instead. It will need some adjustment, but should look ok when done, certainly better than no interior!

I'm not yet sure if i'll dcc it yet or not, depends on the chassis and my limited electrical knowledge. So, I will post updates here for anyone interested in the build and will be no doubt asking for some advice from you during the build.

 

Thanks, Stuart.  

[dmustu]

Got the chassis built, was quite easy to do as it all screws together. I have decided not to dcc it at the present time, getting the motor connected to a decoder looks pretty straightforward, as it is connected to the chassis by 2 wires. Disconnect the wires from the chassis, red and black decoder wires connected to the chassis, orange and grey ones to the motor. It's the lights i'm not to sure about at the moment. 

Edited January 5, 2018 by dmustu

[dmustu]

[kvp]

That's a really nice kit! For the lights, it looks like 4 contacts for 2 light types (head/tail). Just disconnect the pads from the main board copper and solder in the 3 wires from the decoder. (power to 4 pads, forward and reverse to 2-2) On the other hand you can get really fancy and get a 5 output decoder for having separate functions for each light and one for the interior. This would avoid the need to wire in the two switches somehow to disable the lights on a coupled end. (they would have to go in series with the power feed wire going to each end)

[dmustu]

 I have been working on body construction.

Thanks for the suggestion Kvp, i have played around with the lighting kit, but it is not really suitable for dcc. The lights connect to the chassis with a 4 pin plug, testing the pins with a transformer, the head and tail lights are not wired up as expected.

 One pin is a common return, one is connected to the tail lights, one to headlights, one to interior lights.        Connect a positive wire to the common, negative to the other 3 will give headlights one end, tail lights the other and interior lights. To get the lights to change direction, reverse the polarity. From what I can workout, connecting these to a decoder means that you will only get correct lighting in one direction! It's a pity that one pin only does red lights, one does white, if one pin did white one end, red the other, then dccing the lights would be easy.

 Completed bodyshell 

 

 

[kvp]

17 hours ago, dmustu said:

Connect a positive wire to the common, negative to the other 3 will give headlights one end, tail lights the other and interior lights. To get the lights to change direction, reverse the polarity. From what I can workout, connecting these to a decoder means that you will only get correct lighting in one direction! It's a pity that one pin only does red lights, one does white, if one pin did white one end, red the other, then dccing the lights would be easy.

One fix seems to be to swap the polarity of the white leds on one panel and the red ones on the other. Could you post a picture of the led (circuit board) side of both panels? (or both sides of both if they are double sided)

[dmustu]

Hello KVP, the kit is not the easiest thing to photograph, but here you go. Interesting idea swapping the polarities, but i'm not sure how easy it would be to do, as the kit is a long thin circuit board, coated in white plastic covering.

I decided to carry on with assembling the kit, removing the lights to mod for dcc will be straight forward, if possible to do.

 

[dmustu]

And here's the kiha 40 kit completed. Although the kit itself is complete there's still some work to be done on the model, I still need to do some work on the interior, add some details like windscreen wipers and air pipes, reduce the brightness of the interior lights, add weight to improve the running qualities as the model is quite light, and some light weathering to complete.   

Edited January 27, 2018 by dmustu

[Kiha66]

Wow, nice work!

[kvp]

I think i have a solution, but it's a bit bulky. Maybe in H0, you can fit it in. I would add a small low current relay with a single seried diode to each light output (light positive blue to one coil terminal the white or yellow to the other). Then feed the track DCC power (red wire) to the light common and the black to the interior lights. For the headlights route the red wire to the relay's common terminal and add a small diode the NO connections, opposite directions for each relay. Then connect the outputs together and to both the head and tail light inputs. This means an active low on the white will send a half rectified DCC signal (a DC wave) to both the head and the tail lights and an active low on the yellow will send the reversed polarity half rectified DCC to head and tail. The side effect is that both the head and tail lights would light up together (on the opposite sides). Using 4 decoder outputs and 4 relays for having a dedicated pair of relays for the head and tail lights would also work, but might be too much circuit to fit it. I think by getting small smd morse relays rated for 16-18V but pickup at 12V would work. The nice thing is that this circuit does not require any modification to the light circuits, just the isolation of the light connector pins from the main board. For dimmer interior lights, just add a resistor to the interior lights input between the track power connection.

 

Required parts:

two low current small relays (morse 16-18V with at most above 12V pickup)

two standard diodes

interior light dimming resistor (could be variable or fixed)

some short wires

 

ps: You can glue (hotglue or double sided tape) the two relays on their back to the baseborad and solder to the legs on top.

 

An alternative would be to use a motor driver ic to convert the two low active signals (white and yellow) to reversed polarity, but that would need a decoder with both power (blue) and ground wires and two pullup resistors for the two driver ic inputs. (power to the ic and two pullups, ground to ic, connect the two decoder outputs to the two inputs together with the pullup resistors, then the ic outputs to the common and the other to all 3 inputs) This would give a smoother light due to using the decoder's DC filter to power everything. Any motor driver H bridge drive ic rated for the DCC voltage and the low led currents would do. No mods on the lightboard either.