Electronics Tutorial Anyone?

Discussion in 'Tutorials' started by redpiperbob, Jul 31, 2018.

  1. redpiperbob

    redpiperbob Full Member

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    Hi All here is the start
    First how to disassemble coaches
    Here are several coaches two each of Bachman and Hornby.

    This first one is a Bachman no screws it just unclips.

    First insert the some credit cards or something similar as shown one in the middle and one at each end on both sides.


    Then lift the chassis upwards as you hold the body
    This is the end we shall fit the board into as it has space and has frosted windows so you cannot see the board.
     
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  2. redpiperbob

    redpiperbob Full Member

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    The next one
    Bachman Two Screws

    This type is more involved
    First remove the screws marked with the red arrows then carefully remove the bogies from the chassis. I say carefully as the coupling parts are loose with only a spring to hold them in position and the whole assembly can come detached. As in the next picture.

    The red arrows show the position of two more screws to remove. Once these two screws are removed I suggest that you screw the bogies back on this will allow you to handle the coach for the next steps.

    Next we need to remove the water filler pipes (1) from the holes (2) in the ends of the coach there are two at one end and one at the other.


    After this we need to open out the coach sides at the bottom as the red arrows show then lift out the seating fame.


    The separated parts. Be careful of the clear injection moulded windows as they are only clipped to the coach body.

    And once again the board will be fitted in the lavatory end of the coach.
     
  3. redpiperbob

    redpiperbob Full Member

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    The next is
    Hornby no screws
    First unclip the bogies from the coach chassis.
    Press the tabs in one end of the coach chassis while pulling up on the body to separate . then do the same at the other end.
    The coach chassis and body will separate as above.
    We can put the board in either end of the coach as there are blind spots at both ends.
     
  4. redpiperbob

    redpiperbob Full Member

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    Next
    Hornby two screws
    First remove the two screws
    Then press the ends of the roof inwards and lift of the body. Be careful as the sides of the coach are just sitting into the chassis and are not fixed. We shall fit the board into the right hand end of the coach.
     
  5. redpiperbob

    redpiperbob Full Member

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    Tomorrow we shall start the electrics. If you need any more explanation on the coach disassembles then don't hesitate to ask .
    If anything is unclear please let me know.
    Be see you
    Bob
     
  6. ianvolvo46

    ianvolvo46 Staff Member Moderator

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    :thumbup::thumbup:

    ian vt
     
  7. redpiperbob

    redpiperbob Full Member

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    Ok to begin with here is a picture of the DCC to DC converter parts. First I propose to use the bridge rectifier instead of individual diodes. It makes the soldering a little easier. A bridge rectifier is really only four diode in one package..

    From the left Bridge Rectifier, Resistor, Electrolytic Capacitor.

    Next is the circuit diagram
    Now let’s break that down into its component parts

    The first is the bridge rectifier (BR) this component takes the AC (alternating current) and rectifies (changes) it to DC (direct current).

    Now the DCC signal is not a real AC voltage it is more of a switched voltage going from a negative DC voltage to positive DC voltage very fast. There is a lot more on DCC signal here:-

    https://dccwiki.com/Introduction_to_DCC#First_Question.2C_.E2.80.9CWhat_is_DCC.3F.E2.80.9D

    Anyway you don’t need to know exactly how the signal is formed only that if we were to feed that to a LED it would not work. So we need to change the positive to negative voltage fluctuations into a DC voltage. That is the function of the bridge rectifier.

    This is what the bridge rectifier looks like in the circuit

    But the voltage that comes out of the BR is not very regular (not smooth) so if we fit the resistor and the Capacitor in the circuit it helps to smooth out the peaks and troughs. So we end up with about 13 Volts DC out for the DCC 17 Volts in.

    This is what the resistor looks like in the circuit

    This is what the capacitor looks like in the circuit
    Now if you look at the picture above of the bridge rectifier the ~ symbols on the left are the DCC input pins it does not matter which is connected to which rail.



    Then we need to connect one end of the resistor to the + pin of the bridge rectifier the other end of the resistor has to connect to the positive pin of the capacitor.

    Now it does not matter which end of the resistor connect to the bridge rectifier or the capacitor as it is not polarity sensitive. However the capacitor we are using is polarity sensitive so you will see that the capacitor has its negative lead clearly marked and this must connect to the negative side of the circuit.
     
  8. redpiperbob

    redpiperbob Full Member

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    So now to some soldering

    Well first we have to cut two tracks in the stripboard. These are the ones that separate the pins on the bridge rectifier.
    You can buy a special cutter for this but a 3 mm drill in a pin vise is all you need.

    All the drawings of the board are from underneath

    Then hold the bridge rectifier in the holes in the board and solder in

    Next is the turn of the resistor this is put into the board on end (to save space)

    Then the capacitor don’t forget which way around it should fit The negative lead connects to the "-" rail
    That's all the components fitted to the board. next will be the connecting wires.
    Now is the time to check and double check your soldering joints and if the components are the right way around.
    Please ask any questions you want to. If you want me to go into the electrical theory further don't hesitate to ask.

    Next episode will be on Monday 3 aug
     
    Last edited: Aug 29, 2018
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  9. jakesdad13

    jakesdad13 Staff Member Moderator

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    Wow even a thicko like me could understand that, nice one :tophat:

    Pete.
     
  10. Andy_Sollis

    Andy_Sollis Full Member

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    Actually quite simple.".. simply put isolating fish plates on all 4 rail ends, insuring the power is fed from the narrow end...

    Then feed power to the next lines after your insulating fish plates, and put a switch in one of the power cables between the rail and controller (or bus feed if you have one) but remember to always work to the same rule. I try to just use red and black for track power... “Black to back”so black feed is always the farthest away rail and red is to the front, that way there is no short. You can also put a switch in on the feed to the front of the point... same again at the other end, and hey, you have an isolating loop.

    They aren’t rocket science really.
     
  11. DomMorris

    DomMorris Full Member

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    This is brilliant! Thank you so much, I get the diagrams but being able to read them and then being able to actually create the circuit the diagram depicts seems to be a step too far for my brain. This makes everything so much simpler. Thanks again

    Dom
     
  12. redpiperbob

    redpiperbob Full Member

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    OK so we then the DC connecting wires
    If you use Rad and black wires put the red to the + side of the capacitor and black to the negative side.
    It does not matter about the DCC input wires but I like to keep them the same as the output i.e. red to left and black to right.
    make sure they are long enough you can cut wires easier then extend them. By the way I use thin decoder wire to connect to the pickups.
    Here is a picture of the board in position in the carriage.
    And here is a picture of the pickups I am going to use for the first time.
    and here is a picture of them fitted.
    I had to file down the back of the screw that fixes the pickups to the bogie base.
    And the pickups are fiddly to fit but I got there.

    Be seeing you
    Bob
     
  13. redpiperbob

    redpiperbob Full Member

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    Now for the LED lights First here is a picture of some views of an LED
    As will be seen from the picture the longest leg is called the Anode and is always fitted to the more positive side of a circuit in relation to the Cathode. So in our circuit it needs to be fitted as the following diagram
    As I make the DCC to DC boards in batches I don’t know which board will fit which coach.
    So I make the LED’s and the associated resistor separately to fit which ever coach or wagon I am working on.
    The resistor mentioned above is picked to give the correct illumination . More of this later.
    More LED’s are fitted as in the following
    You will also see the resistor R2 this is picked to give the illumination you require.
    I start with a value of 220 ohms and work up until I like the effect. More resistance less light.
    I usually make the led strips up to fit the coach. I cut strip board into pieces that are two strips wide and as long as is needed. Here are some strips ripped to the correct width.
    Then solder the LED’s into place five or six seems to be enough as below
    solder the LED's to the stripboard with all the long legs in the same side i.e. the left.
    these are the legs that will be connected to the red wire coming from the board But first we need to add the resistor mentioned above. The other side of the stripboard is connected to the black wire coming from the board.
    here you see the LED's fitted to the coach see how the resistor is mounted at the end of the strip.
    and a view of the other end.
    The Stripboard is now glued to the coach roof. I use hot glue. And the coach is reassembled.
    That completes this Tutorial if you have any questions or something is not clear then please ask away or PM me.

    Be see you
    Bob
     
  14. redpiperbob

    redpiperbob Full Member

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    Next Basic DC wiring give me a couple of days to recover :facepalm: :cheers:
    Be seeing you
    Bob
     
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  15. Splitpin

    Splitpin Full Member

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    Thanks very much for this great tutorial Bob, it's right on topic for me at the moment as I'm trying to arrange occupancy detection at the ends of my trains.
    As a start I've been working on a brake van and bought a 6-pack of tiny tail lights from DCC Concepts and their axel/spring pickups.
    Their instructions were all that's needed is a simple circuit: <pickup> - <10K resistor> - <LED tail light> - <other pickup> the resistor/LED order does not matter. So no bridge rectifier or capacitor in this circuit. And this indeed does work - I have a tail light and my occupancy detectors respond as they should. What I don't understand is why or how it works - is it that it's 'half' working - like on/off 50 times a second or so ? Does that matter ?
     
  16. Timbersurf

    Timbersurf

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    Basically , yes. DCC is between 10KHz and 17KHz. An LED IS a diode, so half wave rectifies the supply.
    Basically, no. Although it is only on half of the time, the human eye cannot scan as fast, so just retains it as on (same as TV, fluorescent lights, etc)
     
  17. Splitpin

    Splitpin Full Member

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    Ok got it, thanks for that.
    And a follow up question. Why does adding the LED/tail light into the circuit reduce the resistance of the circuit from what it is with the resistor alone ? Whats happening there ?

    TIA
    John
     
  18. Davoetype

    Davoetype Full Member

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    Look forward to adding some more light to the layout.

    Cheers

    and happy modelling

    Richard
     
  19. redpiperbob

    redpiperbob Full Member

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    Hi All
    has anybody got any requests for the next subject of a tutorial. It seems Matt has his answers to DC wiring.
    If anyone has any suggestions put them here.
    Be seeing you
    Bob
     
  20. redpiperbob

    redpiperbob Full Member

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    OK so here is the next requested thread DC Wiring .
    Now where to start Firstly I don’t know how deeply to go into the theory of electrics. So if you need more detail please let me know.

    First it is convention that if a loco is moving forward on a piece of track the right hand rail (as viewed by the driver) is positive compared to the left rail.
    Now the most DC controllers use 15 volts as the maximum voltage (measured with no load).There is usually a knob or lever on the top of the controller this alters the voltage from 0 volts to 15 volts .
    This means the lower the voltage the slower the loco will run.as the voltage increases the loco speed increases.

    Here I have added a red arrow and a black arrow to show the feed of the controller. The red arrow will represent the positive electric feed and the black will represent the negative or 0 voltage or return of the controller.
    Here are the names of some of the parts of a point.

    Now we have to look at the way a point (switch) is wired.
    The frog on a electrofrog point is connected to the blades and changes polarity when the point is switched .
    The frog on an insulfrog point is isolated from the rest of the point.
    Now if we add a electrofrog point into the layout.

    When the point is set for straight on the right hand blade is connected to the right hand rail (positive) and the frog which is now positive also. When the point is switched to the siding the left hand blade is connected to the left rail (negative) and the frog which becomes negative.
    With DC control this makes no difference to the wiring as when the point changes route the current to the track beyond the point changes too.
    Now I have drawn up a layout. Hi Matt I hope you do not mind me using your planned layout as an example.

    Here it is. A main line, a loop, and a siding. Now Matt wanted to have an isolated section at the toe of point 1 as in the following picture.
    You will notice I have changed the track feed from the controller to the right hand side. This is to simplify the overall wiring. The red wire A is fed from the controller through a single pole, single throw switch. When the switch is open the loco is isolated from the rest of the track. The gap in the red rail is filled with a isolating rail joiner. The feed B is to overcome the insulating rail joiners to allow for isolated sections. As explained in the next section.
    Now we may want to have a loco in the siding and run another though the main or the loop without effecting the one on the siding. To do this we just need to fit another switch and isolating rail joiner into the circuit as in the next picture.

    I have added 3 more breaks in the track to expand the capabilities of the layout. Now we can isolate locos on the loop and the siding. The gap in the red rail below 1 is to allow the point 2 to be at a different setting to the point 1 i.e. point 1 straight on point 2 thrown.

    The next diagram shows the complete wiring for the layout.



    So with just 3 single pole single throw switches we can control the whole layout.

    Next we connect the solenoids for the points.

    If anything is not clear please ask away.
     
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