Ok, so let me start by saying im really a neophyte at all things electronics. I've soldered a bit and tinkered with stuff but nothing really to write home about. On my layout i want to have 2 handheld throttles and because im a bit of a fuddy-duddy i want them both identical. Alas, my MRC cab control with PC is one of a kind it seems and it means in order to have 2 identical throttle ill have to build them myself.
nows heres the one im looking into
http://www.awrr.com/throtl5.gif
now a couple things confuse me, the worst offender is that little upside down triangle that means to ground...now what th heck does that mean??
also i know a potentiometer has 3 little tabs, but which one connect to which?
also looking at the circuit, between R5 and R6 theres a serie of little inverted V what are those?
whats the lil squiggle under R4?
any idea how big this throttle is when fully built? as big as a pack of cigarette? size of an altoid tin?
thanks
At least I can tell you that those inverted vees by r5 & r6 indicate a plug and socket.
this is where you would have a polarized four pin plug and socket like a Molex connector.
The bill of materials shows R4 to be a linear pot (potentiometer) that would be a slider pot like the type used on a graphic equalizer. Usually a wiring diagram will show an arrow pointing to a coil to indicate a variable resistor or potentiometer.
ED
The 'upsuide down' triangles indicate the circuit ground or common. All points with those symbols should be connected together. Imagine how complicated the drawing would look if those lines were shown.. The arrows between R5 and R6 indicate a plug and socket - R3, R4, R5, R7, SW1 and SW2 can be mounted in a seperate box and tethered to the rest of the circuit to give you a walkaround handheld control. One thing missing - you need FIVE pin sockets not jus thte 4 shown because you have to pass that pesky ground through as well.
The little squiggle under R4 indicates it is a potentiometer, not a regular resistor. Contrary tot he above, a 'linear pot(entiometer)' does not mean one of the straight line ones like a stereo control. The 'linear' refers to the resistance change as you move the center wiper over the range. IE, you have 0 resistence at on extreme, turn the knob halfway and you're at 50% resistence, all the way up is 100%. The full name is 'linear taper' The other choice is an 'audio taper' or logarithmic, where the amount of change is greater at the low end and less at the high end. Commonly used for volume controls. Either type can be had in either the knob type that turn or the lengthwise slider type.
The biggets part in there is probably the relay. You need space for the toggle switches and potentiometer so it would be a bit larger than a cigarette pack. If you're new to this, don;t try to make it as small as possible, give yourself some room to work. If you built is all in one box, you don't need the plug and socket bit, that an extra if you want to make a walkaround - and in that design the full train power would not go to the handheld part. If you put it all in one box it would probably get a bit warm depending on how much current your train draws. Plus you should use a heat sink on the transistor which will make it bigger.
I don;t quite get the 'double R1 if you use a green LED' thing. The green LEDs I've seen have the same voltage drop as the red ones and the same current rating so they'd use the same resistor. Check the ratings on whatever you buy, or just use the specified red ones for no issues.
--Randy
Modeling the Reading Railroad in the 1950's
Visit my web site at www.readingeastpenn.com for construction updates, DCC Info, and more.
When you say: " connect all of them together" does that mean to just bunch all the wires together and solder it in one big blob?
Ok now i guess im not completly ignorant because i had figured out what a linear pot was. As for the inverted V i guess it makes a lot of sense. the "main unit" can be stationary while the speed control, direction and momentum can fit in an hand held device that is tethered to the "main unit"
now, umm, whats the relay for and how come the mometum doesnt have a simple SPST switch? ooh and if i use a heat sink is it still safe to house it in a plastic project box?
Those are a pretty slick little throttle .... I built two of them for my layout before I converted to DCC.
Keep in mind, the only components in the actual hand-held are the items at the bottom of the cord connection. I didn't add the momentum feature, so the only parts in my hand-held were R3 / R4 / R5 / SW1. I used an old 35mm film canister for the hand-held and used a four conductor coiled phone cord to attach it to the base module (six conductor coiled cords are also available IF you want to add the momentum). The rotary pot was mounted on the bottom of the canister and the switch was mounted on the side giving it extremely good one-handed operation. A phone jack was mounted to the cap so the coiled phone cord could be plugged into it.
The rest of the components can be mounted on a board and mounted under the bench-work.
Mark.
¡ uʍop ǝpısdn sı ǝɹnʇɐuƃıs ʎɯ 'dlǝɥ
rancheroWhen you say: " connect all of them together" does that mean to just bunch all the wires together and solder it in one big blob?
Short Answer: Yes
Long Answer:
Ground means they all go to ground, which is - supply terminal typically on the DC power supply. If you will note, one of the grounds connects straight to the - connection point. So when you connect all the grounds together, you get a connection to the - terminal.
Don - Specializing in layout DC->DCC conversions
Modeling C&O transition era and steel industries There's Nothing Like Big Steam!
ranchero When you say: " connect all of them together" does that mean to just bunch all the wires together and solder it in one big blob? Ok now i guess im not completly ignorant because i had figured out what a linear pot was. As for the inverted V i guess it makes a lot of sense. the "main unit" can be stationary while the speed control, direction and momentum can fit in an hand held device that is tethered to the "main unit" now, umm, whats the relay for and how come the mometum doesnt have a simple SPST switch? ooh and if i use a heat sink is it still safe to house it in a plastic project box?
Yes - although it's usually more convenient to run pieces of wire between all the points. And neater than one big blob.
The relay is for reversing. The contacts are wired like a DPDT switch. If you just put a DPDT switch in the handheld part, full track current would have to run on those wires, plus you'd need more wires. Using the switch in the handheld to turn the relay coil on and off means only 2 wires, and low current.
The momentum uses a SPDT because if you just turned off the capacitor, it would discharge very slowly. If you would then turn momentum back on while the capacitor was still mostly charged, your loco could suddenly jump in speed. Using the SPDT, the 'momentum off' position actually shorts the capacitor via R7 to discharge it fairly quickly. No you can't just short it out, it would arc the switch contacts and wear them out.
You can manage this - just do NOT deviate from the instructions unless you really understand what the components do. You can build electronic circuits that work even without a complete understanding of the theory if you trat the components like puzzle pieces. Each one fits in exactly one place, in one way. Once you understand how it all works together, you can make alterations or sustitute different parts. FOr example, the way that is designed, you can't unplug the handheld portion and allow your train to keep running, it will stop. Once you understand the theory, you cna add components that will allow the train to keep runnign while you unplug and move to the next plug in location.