Through research on this site, I found the link to
http://home.cogeco.ca/~rpaisley4/CDPSU.html
I want to build the 2nd one from the top for my atlas turnouts. However, there are no part numbers for that diagram. Further down the page, in the other diagrams, the author uses these parts:
-transistor 2N3055
-diode 1N4001
-capacitor 2200 ufd, but no voltage rating
-various resistors.
I found the transistor at the link below, but it doesn’t look like it has 3 prongs…could be a bad camera angle.
http://www.allelectronics.com/cgi-bin/item/2N3055/search/NPN_TO-3_TRANSISTOR_.html
Could someone verify these part numbers will work. I would also appreciate a proper voltage suggestion on the capacitor, and the proper size and watt rating for a resistor.
I plan on powering 2 turnouts from one toggle switch occasionally. I don’t see myself wanting to do more than 2 turnouts from one toggle switch for now. So should I get a bigger capacitor? or will that one do.
I have a few huge capacitors from an old air conditioner system. These things are the size of a tall coffee mug. Maybe I should experiment with those. [#wstupid] Just kidding folks.
If anyone looks up part numbers, please do so at the www.allelectronics.com website. I still need to order those SPDT momentary switches from them, so I’m gonna wait and do one order.
Thanks again.
Off the top of my head -
The diodes are standard parts, and they are used to rectify the power input. If you are using a DC power supply, these are not required and will drop the output voltage by another 1.5 if included. AC power input - 16 Volts AC is great - should be preferred, though. Diodes should be rated 50PIV (peak inverse voltage) minimum - 25PIV is marginal.
The same for the capacitor(s). They need to be rated 50 volts and not 25 volts. A single 2200 ufd cap should be sufficient to drive at least 2 Atlas switch machines (unless you only have a 12 volt DC input). Adding another 2200 ufd capacitor in parallel, or a single 4000+ ufd cap would be overkill in your case, and would increase recharge time.
I can’t tell you much about the transistor without more research, but it should be a pretty generic part. None of the values of these components are particularly critical except having a high enough voltage rating to handle peak voltages of the extreme case of an 18 volt RMS input.
yours in wiring
Fred W
Thanks Fred.
I am currently powering my switches from an old computer power supply. I’m using the 12V line, which is DC. Would you suggest two of the 2200 ufd capacitors in parallel?
Brian
The top drawing is an example of the circuit. In the second drawing, and the text under, all of the information needed to build the circuits is given. He combines both types of circuits in the drawing (pick which one you want to build).
I use a circuit similar to the non-transistor version and it works great for me.
2N3055 The case is the third connection. It will be the collector. In this application you will not need a heat sink. Just use a #6 screw and connect to one of the mounting holes.
You lost me Ned.
I modified that picture, and put 3 arrows pointing to the leads of the transistor. Which arrow in the picture represents the “collector”/case?
Picture link: http://www.converttapes.com/logic.jpg
#1 is the base, #2 is the collector (CASE) and #3 is the emitter. When you get the transistor hold the case with the pins pointing toward you. You will note the two pins as being on one side of the centerline or the other. Rotate the case so the pins are below the centerline and the emitter is on the left and the base on the right and the collector is the case. Hope this helps!! Mount the transistor so the case does not contact any other parts. The case style is called “TO-3” . Sockets and mounting hardware are sold for TO-3 transistors that may be helpful
Thanks Ned. That cleared it up.
Brian
The old computer power supply will put out a regulated, filtered 12V. No ripple or AC peaks to boost the capacitor charge (and output) voltage. In light of this, I would probably add the 2nd capacitor and test with some of your Atlas switches. If the switch throws so hard the points bounce back, then you have too much capacitance. Just remove the second capacitor. But my best guess is that you will want the second capacitor.
Atlas switches (turnouts) have relatively low friction throws and no latching springs. Atlas switch machines are relatively low power (compared to other brands of twin coil switch machines) and have a weak latching system (compared to other switch machines). So “bounce” is possible if the machine throws with too much authority. Testing will tell you what you need to know.
Bypass or do not install the diode bridge on the input of the circuit when using a 12V DC source for power. The bridge will lose another 1.5 volts to rectify what is already DC. But most of us only build one CD unit in a lifetime, and move it from layout to layout. So putting the diode bridge in, but bypassing it for now, would allow you to use your CD unit with another power source at a future date.
The capacitors only need to be rated at 25 volts if being used with the regulated and filtered 12V DC source. But again, if you ever want to use it with an AC transformer for input power at some later time, you will wish you had the higher rated capacitors (50V).
just my thoughts
Fred W
Thanks for the detailed response Fred. I’m sure one day I’ll move to nicer switch machines, but for now, the atlas switch machines will do. I want a CD unit so my son doesn’t kill one.
I’m also going to be adding turnout direction signaling, so we can eyeball which direction the switch is thrown via LED. All of this helps a young child.
Ok, I redrew the image, I removed the diode, and placed a 2nd capacitor. Could ya’ll verify this is correct? I’m still guessing on the resistor. Nobody commented on the resistor.
If you scroll about 1/3 down that page on Rob’s site you will see the detailed version of the circuit with all part values called out. It’s in a block of two circuits which are otherwise identical except the second one has an extran transistor, LED< and 3 resistors to form a ‘charged’ indicator which isn’t really necessary. You will notice int he circuit I am referring two there are TWO resistors, a 2.2K and a 10 ohm 5 watt. The 10 ohm serves to limit current flow if you hold the button down too long or a button sticks. The basic design at the top of thepage does not have this. The circuit I am referring to is pretty much identical to one I built from the book Practical Electronic Projects for Model Railroaders (I’m sure this is out of print), and used with no problems on my N scale layout. For HO add the second capacitor in parallel as you have done and you should have plenty of power to throw Atlas HO scale switch motors.
On most electronic parts sites, you can key in the part numbers in their search and it will show you the exact part or equivalent. I usually use Mouser because they didn’t have a surcharge for a small order, but I saw someone post elsewhere that this may no longer be true - I haven’t ordered anything in over a year.
–Randy
Thanks. I updated my picture…minus all the diodes. I’m leaning towards no diodes because of a previous poster stating it will lower my voltage. I’m starting with 12V, so I don’t need any voltage drops.
You want to keep the diode on the right side of the diagram - it prevents the “back” voltage spike from the switch machine coils from damaging anything.
The 4 diodes on the left are for rectifying an AC power source to DC, and can be eliminated or bypassed if using a DC power source. The input diodes do drop the input voltage by 1.5V, so in your situation bypassing or elimination is advisable. Bypassing, but keeping them there, allows you to reconfigure for an AC power source later on. Or you can add 4 diodes or a full wave bridge at such a time, too.
yours in wiring
Fred W
