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 Re-wire WIP / Tutorial of sorts for Electronics (Medical Backpack) (pic heavy)

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Sarr Vok


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  • I reject your reality and substitute my own!
As some people from my Clan (Twin Suns) may already know,
that my Medical Backpack's wiring is a mess (all because I wanted to get it finished before a convention #Relatable).
So it needs re-wiring for safety and to make it nice and clean. So Iíll be made this tutorial of sort for the wiring of my Medical Backpack (not the backpack itself, I sadly donít have enough pics for that)(also a little pic heavy), I'll be going through how to plan, prepare and wire LEDís (light emitting diode), LED-strips and switches step by step.



So, first of all, we need a look at the tools and materials,

Tools:
I used a Soldering iron (mine is a really old and itís a bit rusty, I suggest not using a rusty soldering iron),
Tin (I use a 0,5 thick roll of tin),
wire cutters,
small pliers,
glue or hot glue (the last two are for making a small Sintra frame for the LED-strips),
Sandpaper (high grit),
 (optional) Helping hands (a little stand with little clamps (again Iím not sure if thatís the right word, hereís a link so you can see what it is :https://www.amazon.com/s?k=Helping+Hands&ref=nb_sb_noss ),
(optional) a makeshift LED/circuit tester (I made a tester using the 9V battery and holder by just attaching a blue cable for the Ė and black for +),



The materials:
Wire of 0,5 mm,
LED's (Forward Voltage: 3.2-3.4V depending on colour),
resistors (440 ohm),
LED-strips (12v) (white and blue),
Sintra,
Switches,
9V battery,
9V battery holder (mine was salvaged from some kids toy),
Acrylic plastic and bond paper(or tracing paper, baking paper) (to defuse the light of the LED-strips),

Note:
  • If possible I would suggest having different coloured wires for the + and - (or a more complex colour code if you have the colours). I'm going to be using whatever I've got so all the wires are salvaged and different colours.
  • Another thing to note is that I'm using a 9V battery instead of a 12V power source (because thatís all I have at the moment), the LED's will have resistors so that it can run on a 12V circuit. The LED-strips will technically it will work on 9V but it will not be as bright. I plan to replace the 9V battery it the future, so if you or going to use this tutorial keep that in mind.
  • DON'T let 9V or 12V directly flow through the LED's without the correct resistor in front of it, doing so will break the LED (the LED-strips don't need an external resistor do to them having an internal resistors build in)


Step 1, planning and preparations:

Plan out where you want your LED's, Switches and LED-strips and what colour you want. once I knew where and what, I made a sketch and a diagram for it (forgive me if itís not the correct or right technical word, my English is good but my technical English is non- existing. Iím actually almost finished studying to become an electrician so I know the technical words in Dutch do to living in Belgium) I split it into two parts, the top and bottom, I started with the top because the battery and main-switch are just behind the top part and in my opinion it's easier to start from the main-switch or battery.



Like you can see on the image below, I've divided the four external switches into different circuits (A,B,C,D) and numbered the LED's and LED-strips with the corresponding circuit (by example: A1,A2,A3,...) I've also coloured the LED's and strips on the sketch to have an easy with to remind myself what goes where and what colour. Some advice to make it easier, write on your project itself where stuff it, by example LED A1 and switch A have there number and circuit letter written above, under or beside it.



Also It's worth keeping in mind where you want your LED's, switches,... when making your project (my example is my Medical Backpack). It is really really handy (if possible) if you can open or access the internal parts of your projects, instead of gluing it all shut and not able to opening it without breaking you prop or costume. For wiring, repairs, bragging and showing off the internal parts, for putting chocolate in your Medic backpack (because chocolate is good medicine),... and also for re-wiring, it is really handy to take off the front panel (that's attached with magnets) of my backpack to rewire everything. So plan it so you can open it up or at least keep int in mind when building something.

Resistor:

Now keep in mind that the individual LED need 3,2 Volts, so to prevent the LED from breaking you'll need to place a resistor right in front or right behind the LED with the correct resistance. To calculate how much resistance (and to then get the right resistor with the correct value) you'll need to use Ohm's law, Now here is where it gets too hard for me to translate my knowledge in to English without copying someone else's explanation. So here's a Video on
YouTube that explain what you need to know to detail, [video here: https://www.youtube.com/watch?v=NfcgA1axPLo ]

but basically to find R (resistance) you need to use this formula:
R=(Battery voltage - LED voltage) / desired LED current (A)

By example my LED's are 3.2V, desired current is 20mA for LEDís (or 0.02A)(use A not mA in the formula) so my calculation is R=(12V-3.2V)/0.02A = 440 ohm.



LED's and LED-strips: Parallel and Series,

Just like general lighting, we'll need to decide if we are going to put the LED's and LED-strips in parallel or series. Parallel and Series are the ways you put them in a circuit, there are pros and cons with both of them. I'll start with explaining series (because itís easier), series is putting your user (again sorry I don't know if it's the right English term) one after another, by example: the end of Lamp 1 goes to the start of the Lamp 2, the end of Lamp 2 goes to the start of Lamp 3,Ö
The pros: the I (Amperes) is constant over all the users, formula:
   I-total = I1 = I2 = IÖ
The cons: the U (Voltage) gets split between all the users, formula:
   U-total = U1+U2+UÖ


Parallel is where by the + are connected with the other + from 2 or more users and the - are connected with the other - from 2 or more users. by example the + of Lamp 1 and Lamp 2 are connected and the - of Lamp 1 and Lamp 2 are connected.
The pros: the U (Voltage) is constant over all users, formula:
   U-total = U1 = U2 = UÖ
The cons: the I (Amperes) is split between all the users, formula:
   I-total = I1+I2+IÖ


Mixed is another way to place users, simply said itís a mixture of Parallel and Series.


In general for users Parallel is what you want to go for, but it's likely to become a mixed. I put the Resistors in Series with the LED's, Because ohm's law is in place U = I . R , basically is the R (Resistance) is higher and I (Amperes) stays the same then U (Voltage) will be smaller, in this case they need to be in Series to active a lower Voltage for the LED. but the rest will be in parallel to not lower the Voltage for all users. (ďfunĒ fact: LED-strips are built in parallel, the small LEDís in a strip are parallel over each other.)


Acrylic plastic:
Now for preparation for the wiring, I would cut the Acrylic plastic to the size you need for your LES-strips. after doing that sand one side (or both sides) with the high grit sandpaper until it's no longer see through. the reasoning for this is for defusing the light of the LED-strips, and the bond paper (or tracing paper or baking paper) are for further defusing of the light.



It's also a good idea to have your tools and materials close and ready to use.
I will be starting with the Top panel first do to it being right in front of the battery and main-switch.
know that all that is said let's go to step 2.


Step 2, Clean up:
Remove all the wires, from the switches, LED's,... and clean up the switches and LED's by taking the big blobs of Tin (if you are like me and youíre not the best at soldering).

Note that I'm not going to re-use the 1,5 mm wire that I used the first time, Because they were thicker then they needed to be and they were a less or non-flexible. So I'll be using 0,5 mm thick wire and flexible wire so that I can easier bend/move it out of the way of the other things.



Step 3, wiring and soldering top panel:

Now that I've removed all the mess I can get to work, First I soldered the 440 ohm Resistors to each of the - pool of the LED's (Note: the LED-strips have internal resistors fo,r 12V). After that I started on the first circuit (Z) (the following requires you to go back and forth between your sketch, diagram and soldering). This circuit is right after the main-switch and has two LED's that are in parallel over each other.
Z1 is actually a button with a build in 12V green LED, I'm using it because it looks cool but the button has no use.
Z2 is a standard red LED.

Then I Soldered wire's from the - pool of Z1 to Switches A, B, C and D on the middle pin (some switches have 3 pins, in that case always take the middle and one of the side pins).
then Soldered a wire from a side pin of switch A to resistor from A1
Soldered a wire from a side pin of switch B to resistor from B1.
Soldered a wire from a side pin of switch C to resistor from C1.
Soldered a wire from a side pin of switch A to resistor from D1.
(Note: 1. I've placed the resistors on the - pool of the LED's.  2. Use the same side pin per switch otherwise youíll be switching between LEDís instead of putting the LEDís on or off).

Then to finish off the A1, B1, C1 and D1 LED's, I soldered wire's from the + pool from A1, B1, C1 and D1 to the + pool From Z1. At this point I would suggest using a LED/circuit tester to test the LED's (from the resistor to the + pool of the LED), the switches and the current wiring that you've just soldered. It's a good idea to test every so often after you've soldered parts of a circuit.
Then I went through the rest of circuit A (A2 and A4). To do that I needed to make a frame out of Sintra for the LED-strips, this is where the glue or Hot-glue comes in. Make sure to use something to dived the LED-strips (in this case with Sintra), if they're a different colour. After making the frame for A2, C2, B2 and placing them in the frame.



then I soldered a wire from switch A middle pin to LED-strip A2 (- pool), then I soldered a wire from LED-strip A2 (+ pool) to LED Z1 (+ pool) (I'm using Z1 + pool to connect it parallel).
Next is LED A4 (because LED's A3 (3.1 and 3.2) in on the bottom panel and the bottom panel I will be doing after the Top panel), I soldered a wire from side pin A to resistor from A4. Then I soldered a wire from the + pool from A4 to the - pool From Z1.
Then I soldered a wire from switch B side pin to B2 ( - pool),
then soldered a wire from B2 ( + pool) to Z1 ( + pool).
Then I soldered a wire from switch C middle pin to C2 ( - pool), then soldered a wire from C2 ( + pool) to Z1 ( + pool).
One more LED for the top panel, I soldered a wire from side pin D to resistor from D3. Then I soldered a wire from the ( + pool) from D3 to the ( - pool) From Z1.



Now to finish off the panel. I used bond paper to further defuse the light of the LED-strips, by having multiple layers you will be able to defuse the light even more. Before I glued the frame to the panel with hot-glue, I tested the circuit and double checked the LED-strips. Then I simple glued the frame to the panel (with hot-glue).


Logged
Combat medic at your service:
OM #2462 | O.O.P.S.! #53 | QMU #82 - Lobster dog!
   

Sarr Vok


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  • 275
  • I reject your reality and substitute my own!
Step 3, wiring and soldering (Bottom panel):

Next is the bottom panel... it's also a mess... we've all been there.
So first I remove everything and clean it up.



on the bottom panel the LED's and LED-strips are wired in four groups, A (A3.1 and A3.2 LED's), B (B3 LED), C (C3 LED and C4 LED-strip), D (D2.1 LED and D2.2). I started like with the top panel with soldering the resistor to the - of the LED's. I started like with the top panel with soldering the resistor to the - of the LED's. This time I soldered wires that connected the + pools of the LED's and LED-strips together, because the switches are on the - side anyway and it makes it easier with the cable going to the Top and Bottom panels.

Then I started with group A (The A-Team), I soldered a wire from A3.1 resistor to A3.2 resistor. Then soldered a wire to the CTB* (A) from
A3.2 resistor to A switch side pin. So next I soldered a wire from A3.1 + pool to A3.2 + pool and then the CTB + wire.
Next group B, is only one LED so I soldered the CTB + wire to the + pool from B3. Then I soldered a wire to the CTB (B) from B3 resistor
to B switch side pin.

*Cable going to the Top and Bottom panels
- It has cable A,B,C,D and general wire +
- The CTB is a 8 (0.5) wire cable that is hidden in the frame of my Medic Backpack


Now group C, it has an LED-strip and one LED. I soldered a wire from C3  resistor to C4* - pool.
Then soldered a wire to the CTB* (C) from C3 resistor to C switch side pin. Next, I soldered a wire from C3 + pool to C4 + pool and then
the CTB + wire.

*when in doubt use C4 ;)

Now group D, it has two LED-strips. I soldered a wire from D2.1 - pool to D2.2 - pool. Next I soldered a wire from D2.1 + pool to D2.2 + pool.
Then soldered a wire to the CTB* (D) from D2.1 - pool to D switch side pin and then soldered a wire to the CTB* (D) from D2.1 + pool to CTB + wire.
And of course, then i tested it with the circuit tester.




There's only two more this I needed to do at that point,
1) wire the CTB wire's A,B,C,D to switches A,B,C,D side pin and + wire to Z1 + pool.
2) wire the power source (in my case 9V battery, please use a 12V power source if your using LED-strips because may
LED-strips are too dim to see in a lighted room using 9V)
1)Letís get to it. So I Soldered CTB wire A to switch A Side pin.
I Soldered CTB wire B to switch B Side pin.
I Soldered CTB wire C to switch C Side pin.
I Soldered CTB wire D to switch D Side pin.
2)Finally wiring the power source, I soldered the - from the 9V battery holder (without battery)(Never solder live wire's)
to the Main-switch middle pin. Then soldered a wire from the Main-switch side pin to Z1 - pool.
Next I soldered a wire from the + of the 9V battery holder to Z1 + pool.

now double-check, double-test.
and if it works the yeah, If not then take your sketch and diagram and go through your whole circuit.
(Don't be a shamed if it doesn't work the first time. Itís easy to make mistakes with wiring electronics, I speak out of experience).
I hope this Tutorial of sorts has helped you in some way and if you have any questions then I'll answer to the best of my ability (but sadly I'm not an expert... yet).




Logged
Combat medic at your service:
OM #2462 | O.O.P.S.! #53 | QMU #82 - Lobster dog!
   
 


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