I just purchased this power supply here and am wondering if it will work on 12v accessories? Is 13.8v within the limits? I had planned on running my Tortoise machines and lights.
Thanks
Burt
Model Railroading Tips
Call me anal retentive if you like, but when my device is rated for 12 volts I use a 12 volt power supply.
If you use a 13.8 volt supply to power 12 volt light bulbs you will seriously shorten their lifespan.
Dave
Lackawanna Route of the Phoebe Snow
I second the comment.I have the exact same one at home and it is used to power both DCS200 and booster on separate fused circuits though.Being within Digitrax's specs,it is fine for this purpose and I have plenty of power.I'll likely use it for other purposes but will use resistors or whatever necessary to protect the powered accessories.In this particular case,I've read that many modellers use resistors to reduce voltage to their Tortoise motors to slow them down even more for better realism.
Without putting a resistor into the circuit, this power supply would be too strong for a Tortoise motor, and could possibly shorten their life.
A Tortoise would operate too fast on 13.8 volts and might put too much pressure onto the turnout's points without a resistor.
I use resistors even with a lower voltage power supply to slow down the Tortoise.
Using this 13.8 volt supply would be okay with the proper resistor, but you'll have to experiment to find the best value to use.
The Tortoise literature indicates that they draw 15-16 ma at stall. Using Ohms law to compute the resistor value indicates that 186 Ohms would give you 11 volts on the motor, which would be a good starting point; however, 186 Ohms is not a standard, readily available value of resistor, so using the next higher value is where I would start. I think a 220 Ohm resistor would be okay.
I use a 12-volt supply for my light bulbs (inside buildings, streetlights and such) but they are 16 volt bulbs. It's better to run bulbs at lower than their rated voltage, not higher. It gives the bulbs more of a warm glow, they give off less heat, and they last longer.
My Tortoises run on 9 volts. Plenty of power to move the points, and the slower motion is more pleasing to my eye.
It takes an iron man to play with a toy iron horse.
However, if you use an LED in series with the Tortoise motor as an indicator (no resistor needed) this will put about a 2.1 volt drop in the line, so with a 13.8v power supply the Tortoise motor will see 11.7 and it will be fine. Lower though is better for the Tortoise, they run quieter with a bit less voltage.
You can easily drop the output voltage of a DC power supply using some diodes in a series. Use oridinary silicon diodes rated at least the same amp capacity as the power supply, or higher. For each diode in series, subtract 0.6 volts. Just three in series will reduce the voltage 1.8 volts, down to 12 volts. Use 4 or 5 if you plan to connect 12 volt light bulbs as well as the Tortoise motors. With 5 diodes the output will be 10.8 volts, plenty for a 12V bulb, and a Tortoise with LEDs for indicators will get about 8.7 volts, plenty to move and hold but much more quiet than using a full 12 volts. The drop will be constant rather than vary with the load (ok for the purists it will vary slightly at extremes since real-life diodes are not ideal - covering myself for the other EEs out there).
--Randy
Modeling the Reading Railroad in the 1950's
Visit my web site at www.readingeastpenn.com for construction updates, DCC Info, and more.
You can use the below circuit for this. I do.
[url]http://www.electronics-lab.com/articles/LM317/[/url]
Replace R2 with a fixed resistor for the voltage you want.
Great for 1.5 volt bulbs with the proper resistor for R2.
Use the variable resistor for adjusting layout light bulbs, not LED's.
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.
The power supply you purchased is designed to operate automotive electronics (CB radios, scanner, etc). That is why the rating is 13.8 volts. Car batteries are rated 13.8 volts but are referred as 12 volts. All the methods talked about above will reduce the voltage to someting useful. Reducing the voltage below the rating will extend the life of lamps and switch machine motors.
I will additionalyl add that if you can't readily find high amp diodes (Radio Shack lists a 6 amp one, and multiple 3 and 1 amp versions) what you can do is build multiple sets (diodes are cheap) and individually fuse each circuit (recommended anyway). Say one that drops it to 11.6 for Tortoises, with a 1 amp fuse (enough for at least 30 Tortoises - if you have less than that, use 1 amp diodes and a 1/2 amp fuse, good for about 15 Tortoises). ANother that drops the voltage to 10.8 for 12V light bulbs, with a bit larger fuse, depending on how many lights you connect and what the current rating of each bulb is - or even multiple lighting circuits. It's not nearly as complciated as it sounds, it's merely replication of the same thign over and over. 7 amps from that power supply into one spot is enough to melt thinner wire, you are far better off runnign multiple circuits for your accessories and fusing each one to a reasonable level. One big power supply does create a single point of failure and you really should do the multipel circuits - but it can be cheaper than buyign 5 or 6 smaller ones, not to mention easier to shut everything down by turning off one switch instead of 5 or 6.
Thanks everyone for the great information. I think because I'm so new to electronics I might just return the 13.8v power supply and look for the 12v. I do like the idea of lowering the voltage if I can figure that out.
I guess I should also state that all of this is going to connect to my Freemo modular layout. With that said, my DCC and DC Accessory bus run right down the middle; so I'm curious how to hook up one power supply to my lights and another to my Tortoise machines if they a running off of the same DC bus? Should I put a resistor in between my accessory and the feed wire before it gets to the bus?
Thanks,
If you can do basic soldering, the below kit will give you 8 or 9 volts at 1 amp. Just connect it to the power supply 13.6 volts connection.The voltage will remain at 8 or 9 volts, you select which one and will not vary unless you draw over one amp.
Much better than messing with resistors and cost $3.99. This is essentially what I showed you in a previous message.
This really the way to go.
http://www.bakatronics.com/shop/item.aspx?itemid=432
In case the powers to be blip the link, it is sold by Bakatronics LLC, kit FK805 Step Down Voltage Converter
richg1998 If you can do basic soldering, the below kit will give you 8 or 9 volts at 1 amp. Just connect it to the power supply 13.6 volts connection.The voltage will remain at 8 or 9 volts, you select which one and will not vary unless you draw over one amp. Much better than messing with resistors and cost $3.99. This is essentially what I showed you in a previous message. This really the way to go. http://www.bakatronics.com/shop/item.aspx?itemid=432 In case the powers to be blip the link, it is sold by Bakatronics LLC, kit FK805 Step Down Voltage Converter Rich
The solution Rich proposes above is what I do. I use these very same power supplies from Pryamid to run my whole layout. There is one for each of my eight Train Engineer throttles and several others for the signal system and other accessories.
When lower voltages are needed, I tap the power supply with a voltage regulator like Rich linked to. They come in lots of different voltages and/or are easy to build yourself.
Sheldon
I would keep the supply and go with Rich or Randy's suggestion. Both would work well. Radio Shack also offers 12 regulator chips that we've used with good results. The supply you have looks like its well packaged.
Springfield PA
For those more ambitious, I designed a lighting adapter which has multiple outputs and can be controlled from your throttle. It has a fixed 12V output for control panels lights, Tortoises, wireless adapters and similar. It has two 12V on/off outputs that can be used to control street lights and similar lights, which have a fixed brightness. It uses F0 and f1 to control the outputs. Lastly, it has a variable 0-12V output, which running off of your throttle speed setting to power building interior lights where you want to set your own brightness or change it frequently. It uses a mobile decoder that you just assign an unused address. I built two of these for my layout.
Here's the link for more information:
http://www.thebinks.com/trains/decoder_adapter.html
Engineer Jeff NS Nut Visit my layout at: http://www.thebinks.com/trains/
jbinkley60 For those more ambitious, I designed a lighting adapter which has multiple outputs and can be controlled from your throttle. It has a fixed 12V output for control panels lights, Tortoises, wireless adapters and similar. It has two 12V on/off outputs that can be used to control street lights and similar lights, which have a fixed brightness. It uses F0 and f1 to control the outputs. Lastly, it has a variable 0-12V output, which running off of your throttle speed setting to power building interior lights where you want to set your own brightness or change it frequently. It uses a mobile decoder that you just assign an unused address. I built two of these for my layout. Here's the link for more information: http://www.thebinks.com/trains/decoder_adapter.html
Thanks for some good ideas. I just forwarded the link to some Yahoo DCC Groups where there are some advanced DCC users.
Now that's thinking out of the box. Could you post pics and a schematic of the circuit?
Hamltnblue Now that's thinking out of the box. Could you post pics and a schematic of the circuit?
They are there. Click on each picture. That enlarges the pictures that show the schematic and each board.
Download them to your PC. Maybe even enhance then a little for better viewing. It works for me. Very clear. He also includes an email address. Check the whole page out.
Guess it would have helped to click on the link