I've been thinking of this.
My son is bringing up the electronic pieces from the city for me to put in the Capacity Discharge circuit between my transfomer and Atlas snap switch controls.......and the bridge rectifier.
Now, is the bridge rectifier necessary?....the transformer puts out 16VAC and the Atlas switch motors work fine with it that way.....
I can see needing the bridger rectifier if I was going to use the circuit for other things like lighting etc.
Which circuit are you using? The one I built ages ago had a diode int he input so it could be used on AC. The one on Rob Paisley's site needs DC input - large electrolytic capacitors are polarity sensitive as in the transistor used to speed recovery time. If the only diode in your circuit is the one on the output side, you'll need the bidge rectifier.
The CD supply produces a quick strong jolt of DC. The switch motors don't really care. But they will snap with authority and if you hold down the button too long or the button sticks, they won't burn out because the CD supply limits how much current flows once the capacitor discharges. The transistor in the circuit (should probably get a heat sink for it) bypasses the current limit to allow the capacitor to recharge faster once you let go of the button. There are even simpler circuits withotu the transistor but you may not have time to let the capacitor build up charge to operate the next switch, especially if you goof and hit the wrong one and the train is coming.
--Randy
Modeling the Reading Railroad in the 1950's
Visit my web site at www.readingeastpenn.com for construction updates, DCC Info, and more.
I use the below circuit with a diode Matrix circuit for a three way Peco twin coil turnout.
[url]http://www.awrr.com/cdsupply.html[/url]
The ready LED lets me know if the CD supply is ready.
Rich
If you ever fall over in public, pick yourself up and say “sorry it’s been a while since I inhabited a body.” And just walk away.
Sorry, I did an edit in my reply and now the Hyperlink is not clickable. I have seen this before with the new format. Go figure.
richg1998 I use the below circuit with a diode Matrix circuit for a three way Peco twin coil turnout. http://www.awrr.com/cdsupply.html The ready LED lets me know if the CD supply is ready. Rich
http://www.awrr.com/cdsupply.html
it doesn't like the bbcode anymore (the [ u r l ] and [ / u r l ] ) You can just paste in a URL and it 'knows' it is a hyperlink unless it ends with some codes or variables.
I quoted and removed the tags, let's see if this works.
Yup. And now I edited, see if it still works.
One more edit. Strip out the complicated 'ready' circuit and that is the ultimate basic CD supply, somewhat slow on the recharge but super simple in that the circuit is really a couple of resistors and a capacitor. The smaller capacitor is for power suppy filtering.
These two circuits from Rob Paisley are the fast recharge type, the lower one adds a charge indicator with just one transistor and 3 resistors.
http://home.cogeco.ca/~rpaisley4/CDblock.GIF
(left as a link on purpose since they are not my pictures to post)
Yes, you need the bridge rectifier. 60 Hz AC sees the Electrolytic capacitors as a direct short.
The job of the electrolytic caps is to store energy or voltage. For a capacitor to do that, the voltage has to be DC. The bridge rectifier changes the AC into DC.
Elmer.
The above is my opinion, from an active and experienced Model Railroader in N scale and HO since 1961.
(Modeling Freelance, Eastern US, HO scale, in 1962, with NCE DCC for locomotive control and a stand alone LocoNet for block detection and signals.) http://waynes-trains.com/ at home, and N scale at the Club.
Thanks for the responses.
This is the capacitive discharge unit I will be using from Circuitron.
I take it the bridge rectifier goes between my 16VAC 3 Amp transformer and this to turn the current to DC?
No rectifier needed, the Snapper works on an AC input up to 25 volts. In a larger picture you cna see the parts - it looks like diode D1 is probably connected to one of the input terminals to rectifiy the AC input. Notice also there are no polatity markings for the input.
rrinker No rectifier needed, the Snapper works on an AC input ...................... --Randy
No rectifier needed, the Snapper works on an AC input ......................
Thanks, Randy. I just thought of the same thing after I saw the picture. I ordered it without an illustration.....and then thought, Gee, I bet the manufacturer has thought of the polarity issue and probably designed the little board properly. Don't know why I didn't bother to research the product a bit more before posting my question.
From the photo it looks like there is a little symbol by the input terminals that lookslike this ~.
If so, that means that the input is AC. In that case, no other rectifier is needed.
The diodes change the AC to DC voltage.
You can also use DC to power this device. The DC has to be about 2 volts higher than the AC voltage.
I have a couple non railroad devices that work like this and I use 18vdc for them from a couple junk wall warts.
Cisco Kid I've been thinking of this. between my transfomer and Atlas snap switch controls.......and the bridge rectifier.
between my transfomer and Atlas snap switch controls.......and the bridge rectifier.
The transformer is AC most likely. The bridge rectifier will switch it to DC. If you connect the discharge cap straight up the AC terminal, when the current switches direction, your capcitor will lose all it's charge. It would constantly charge/discharge 60x's a second. Soon you'll likely have a greatly overheated capacitor and a non switch coil switch machine.
Randy is correct. No bridge rectifier is needed with the snapper.
Don - Specializing in layout DC->DCC conversions
Modeling C&O transition era and steel industries There's Nothing Like Big Steam!
A transformer by definition is always AC. Anything that puts out DC is a power supply which contains a transformer. Many who are not too aware of electronic devices often confuse these things.
Sometime, connect AC to a electrolytic capacitor and see what happens. I would run fast depending on what the voltage is and how much current the transformer can supply.
richg1998 puts out DC is a power supply which contains a transformer. Many who are not too aware of electronic devices often confuse these things.
puts out DC is a power supply which contains a transformer. Many who are not too aware of electronic devices often confuse these things.
This is true. But I've seen boxes marked as "transformers" from China with DC terminals on the side (along with the AC) that's why I made the stipulation (most likely AC) depending on how he hooked it up.
richg1998 A transformer by definition is always AC. Anything that puts out DC is a power supply which contains a transformer. Many who are not too aware of electronic devices often confuse these things.
Gentlemen, I must correct these statements:
A transformer by definition is always AC. (correct)
Anything that puts out DC is a power supply which contains a transformer (incorrect)
Any power supply that puts out DC has a rectifier. (correct)
Also, it may very well be quite dangerous to connect a capacitor across an AC source as the result may be an explosion.
Any power supply that puts out DC has a rectifier. (correct) and a transformer.