1. Welcome to our site! Electro Tech is an online community (with over 170,000 members) who enjoy talking about and building electronic circuits, projects and gadgets. To participate you need to register. Registration is free. Click here to register now.
    Dismiss Notice

Circuit for 15 Amp DCC Booster

Discussion in 'Electronic Projects Design/Ideas/Reviews' started by krs, May 27, 2007.

  1. krs

    krs New Member

    Joined:
    May 20, 2007
    Messages:
    11
    Likes:
    0
    I'm looking for a schematic for a 15 amp DCC booster.
    DCC as is Digital Command Control for model railroads.

    I can find lots of DCC booster circuits for up to 3 amps; the odd one up to 10 amps, but so far nothing over 10 amps.

    Ideally would be a design with a minimum number of parts.

    - an H-Bridge that can drive 15 amps or better with low on-resistance and short-circuit protection
    - and all the DCC logic done by a microcontroller
    - power would be provided by a 24 volt switching power supply.
     
  2. Hero999

    Hero999 Banned

    Joined:
    Apr 6, 2006
    Messages:
    14,902
    Likes:
    79
    Location:
    England
    It seems like you're looking for a 24V h-bridge motor controller. Please post the 3 A circuit, it's probably easy to up-rate it to 15A.

    Why do you want 15A for? That's 360W at 24V which sounds a lot of power for a model railroad.

    Over current protection can be provided by a polyfuse or resettable circuit breaker.
     
    Last edited: May 27, 2007
  3. krs

    krs New Member

    Joined:
    May 20, 2007
    Messages:
    11
    Likes:
    0
    http://www.electro-tech-online.com/custompdfs/2007/05/booster_1_3_sch.pdf

    This is a DCC booster for H0 scale. The output DCC signal should be 14 volts with a maximum current of 4 amps.
    The H-Bridge used is a L6203.

    I need one for a large Scale model railroad. The output voltage should be 24 volts or close to it and to run three trains I need at least 4 amps each with a little bit of extra current to go uphill - that's how I ended up at 15 amps.
    One can buy commercial DCC boosters up to 20 amps, but I wanted to see if I can build my own using an appropriate powered H-Bridge and a microcontroller for the logic.

    I can't use either a polyfuse or a circuit breaker for the primary short circuit protection at the output.
    Because of the high current, I need something that can shut the power off much more quickly to prevent damage to the model train and it needs to trip just a bit over 15 amps.
    A breaker is too slow and a polyfuse has too wide a trip current range. I might use a breaker as a secondary over current protection device just to be on the safe side.
     
  4. dave

    Dave New Member

    Joined:
    Jan 12, 1997
    Messages:
    -
    Likes:
    0


     
  5. krs

    krs New Member

    Joined:
    May 20, 2007
    Messages:
    11
    Likes:
    0

    OK - we're back in business. The post I thought had disappeared is back and my duplicate one is gone.
    Excellent - thanks.

    Any suggestions as to a reasonably priced, integrated H-Bridge that can handle at least 15 amps continuous and well in excess of 24 volts to replace the L6203?
     
  6. Oznog

    Oznog Active Member

    Joined:
    Apr 21, 2004
    Messages:
    2,879
    Likes:
    11
    Location:
    Austin, Tx
    Doesn't sound like a booster to me. Without special topologies, an H-bridge only lowers the voltage (the term "buck converter" can be loosely applied to it).

    15 amps @ 24V is enough to move an electric wheelchair up a ramp. Unless your electric train weighs over 100 lbs and has a huge motor, I doubt you need this.
     
  7. krs

    krs New Member

    Joined:
    May 20, 2007
    Messages:
    11
    Likes:
    0
    Trust me - this is a DCC booster.

    So are those two here:

    http://home.cogeco.ca/~rpaisley4/HBridge.html

    And yes, I need 15 amps at 24 volts. The whole idea with DCC is that you can control a number of trains on the same track independantly - every train requires about 4 amps, so a 15 amp booster will only allow three trains to run at the same time.

    If you don't know what DCC is, perhaps a bit of reading on the net would help.
     
  8. Hero999

    Hero999 Banned

    Joined:
    Apr 6, 2006
    Messages:
    14,902
    Likes:
    79
    Location:
    England
    Most of use here are familiar with H-bridge circuits.

    I don't see the problem, the datasheet for the L6203 says it can handle 48V at 4A so 24V shouldn't be a problem.
    http://www.datasheetcatalog.com/datasheets_pdf/L/6/2/0/L6203.shtml
     
  9. krs

    krs New Member

    Joined:
    May 20, 2007
    Messages:
    11
    Likes:
    0
    Yes - but I need to run at least three trains of 4 amps each with one booster - that's why I need 12 to 15 amps. The current is the issue - not the voltage, although a higher voltage would be nice because the electronics in the modeltrain engines do generate voltage spikes. But I could suppress those separately if needed.
     
  10. Hero999

    Hero999 Banned

    Joined:
    Apr 6, 2006
    Messages:
    14,902
    Likes:
    79
    Location:
    England
    I understand that but I thought you needed to control the trains independently from one another which is only possible if you use three H-bridges and at 4A per channel the L6203 is perfect.

    I do not know of an IC that's capable of handling more current and is compatible with the L6203. Where are you planning to buy the L6203 from? I would suggest looking in the catalogue or speaking to their technical support line.

    Have you considered using discrete design made with power MOSFETs?

    Current limiting could be implemented by using a current shunt resistor, hall effect transducer or even monitoring the voltage drop across the MOSFETs and turning them all of for a certain periaod of time if the limit is exceeded.

    What's the maximum surge current? You need to either limit it or ensure that the components can handle it and that any electronic fuse won't blow when the motor is started.
     
  11. krs

    krs New Member

    Joined:
    May 20, 2007
    Messages:
    11
    Likes:
    0
    Yes I do need to control the trains independently, but not with three H-bridges, only with one.
    I think the problem is that nobody here is familiar with DCC in Modelrailroading.

    DCC basically places a bipolar signal on the track that is used for both controlling the engines using 8- and 16-bit packets and delivering those at +/- 24 volts and enough current to operate all the motors, lights, smoke, sound etc. on the trains.
    The packets consist of an 8-bit address - a different one for each engine of course, and additional 8- and 16-bit packets to control direction, speed, acceleration, deceleration, whistle, bell, etc etc.
    The DCC packets are generated by a specialized unit called a Central Station (although PC implementations are available as well) and one then needs a DCC Booster to increase the DCC packets to a voltage and current level sufficient to drive all the trains on the layout.
    DCC basically combines the control and the power to run the trains into one single control signal.
    With DCC it's no longer necessary to divide the layout into electrical blocks with lots of wiring and controls, the Central Station encodes the information to be sent to each engine and the decoder in each engine responds to the information sent to its specific address.

    I do have schematics for a 10 amp DCC booster that uses discrete components, but I was hoping to be able to come up with a design that uses a lot fewer components, like basically a 15-amp integrated H-bridge and a simple microcontroller for the few functions required.
     
    Last edited: May 28, 2007
  12. Hero999

    Hero999 Banned

    Joined:
    Apr 6, 2006
    Messages:
    14,902
    Likes:
    79
    Location:
    England
    That sounds like a kind CAN-bus style system to me.

    http://www.yamar.com/DCAN250.html

    Here's my understanding:
    From what you're telling me the h-bridge is not on the power supply to the track but is on board the train. The control signal is superimposed on the 24VDC power supply which is delivered to the train. The on-board microcontroller isolates and decodes the control signals using them to control the on-board h-bridge.

    The current rating of your h-bridge is not the issue, it's the power rating of the power supply. Can't you just up-rate the power supply?
     
  13. krs

    krs New Member

    Joined:
    May 20, 2007
    Messages:
    11
    Likes:
    0
    No, no...wrong understanding.
    The H-bridge I'm talking about is in the booster which feeds the track. There is no control signal "superimposed' on the 24VDC, that's an old model train control concept that never worked very well - with DCC the track power and the control signal are one signal that swings the whole +/- 24 volts and also provides the current to operate everything.

    The current rating of the power supply is not the issue - I'm just going to use a 16 amp 24 volt switching power supply - it's the H-bridge driving the track that is the problem.

    Maybe this very simple explanation of DCC will help:
    http://www.loystoys.com/info/how-dcc-works.html

    I'm trying to build a 15-Amp booster block; there is also an H-Bridge in the decoder in the engine itself. That H-Bridge drives the DC motor in the engine, but that only requires 3-5 amps for Gardenrailroads - that is not a problem, the booster H-Bridge is.
     
  14. Hero999

    Hero999 Banned

    Joined:
    Apr 6, 2006
    Messages:
    14,902
    Likes:
    79
    Location:
    England
  15. krs

    krs New Member

    Joined:
    May 20, 2007
    Messages:
    11
    Likes:
    0
    The second hit on Google is only a 16 volt device; I need something in excess of 24 volts.
    The on resistance also has to be symmetrical on the high and low side so that the power signal to the track is symmetrical to within 0.5 volts at maximum current.
    I'll take a look at the Google hits- but so far I have come up with nothing suitable that way.
     
  16. Hero999

    Hero999 Banned

    Joined:
    Apr 6, 2006
    Messages:
    14,902
    Likes:
    79
    Location:
    England
    Soprry, I didn't notice that.

    Providing the on resistance is low enough not to induce a 0.5V drop then it won't make any difference and considering you can get MOSFETs with on resistances under 30m:eek:hm: these days it shouldn't be an issue.

    If you can't find a suitable h-bridge IC then it's probably better to build a discrete design, that way you can select MOSFETs with desirable characteristics.
     
  17. nfanakis

    nfanakis New Member

    Joined:
    Feb 2, 2010
    Messages:
    2
    Likes:
    0
    Have you seen the trilith series chips from infineon? You can get up to 28Volts @31A but you need two of them since they are half bridges. You will find them in infineon website under Power managment ICs -> Integrated High current motor drivers. I have used them a couple of years back in a motor controller design are the performance was excellent.
     
  18. mneary

    mneary New Member

    Joined:
    Feb 27, 2007
    Messages:
    4,502
    Likes:
    67
    Location:
    California USA
    Three year old thread.....
     
  19. nfanakis

    nfanakis New Member

    Joined:
    Feb 2, 2010
    Messages:
    2
    Likes:
    0
    True. Nevertheless, while searching on the internet I got a hit on it two days ago. It may not have been the info I was looking for but it could be for someone else that will get to this page sometime in the future.....
     
  20. Hexadec

    Hexadec New Member

    Joined:
    Mar 3, 2012
    Messages:
    1
    Likes:
    0
    I'm from the future....:D

    For anyone finding this thread and in need, try: http://www.trainelectronics.com/DCC_Arduino/DCC_Booster/index.htm
     

Share This Page