DIYish DCC Booster Module

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sacto-tt
Posts: 224
Joined: Tue Jan 11, 2011 3:23 pm
Location: Sacramento, CA USA

DIYish DCC Booster Module

Post by sacto-tt »

Like a lot of members here, I seem to have extra time at the house these days. Luckily I can do a lot of work from home, so the paychecks are still rolling in on time.

Since I finally "finished" the wiring in the smaller of the two train rooms, it was time to start planning how to get the DCC setup in place.

Though my DCC system is Digitrax, I'm using Tam Valley Depot DCC Boosters. They are pretty reasonably priced (Approx $50 each) and pretty compact. All you have to do is lay it out and connect a few things. Since I wanted to have flexibility on where I put them and minimize extra wiring, I decided to put together a little self-contained module that I can put almost anywhere.

Here is the Booster layout. It fits on a 7" x 7.5" piece of plywood.
Basic Booster module layout
Basic Booster module layout
Here is a finished Booster with all the components mounted. The DCC In signal is provided via Digitrax Loconet, just plug in a regular Loconet cable. No need to connect it to the track bus.
Booster with all components mounted.
Booster with all components mounted.
Here is the Booster connected to my temporary test loop that runs around the two rooms.
Booster connected, ready for smoke test.
Booster connected, ready for smoke test.
The moment of truth has arrived. It appears to have powered up just fine. No complaints from the DCC Command Station and all LEDs are lit.
Power and DCC system on, three red LEDs, looking good so far.
Power and DCC system on, three red LEDs, looking good so far.
Here it is running a train. Sorry it is HO Scale, but that is the only track I have setup at the moment. Hopefully I can unpack some TT track in the next week or so and give that a spin too.
Here is the Booster in action.
Here is the Booster in action.
-Joe-

dileTTante
Posts: 843
Joined: Wed Jan 06, 2010 12:37 am
Location: Vancouver British Columbia

Re: DIYish DCC Booster Module

Post by dileTTante »

Is there any provision for adjusting track voltage? HO may not be ideal for TT.
For example = https://sites.google.com/site/markgurri ... k-voltages

- Terry C

sacto-tt
Posts: 224
Joined: Tue Jan 11, 2011 3:23 pm
Location: Sacramento, CA USA

Re: DIYish DCC Booster Module

Post by sacto-tt »

No, there is no voltage adjustment. The output voltage is a function of the input voltage. Of course, given that there is no standard to set it to, not being able to adjust the output voltage seems like a non problem to me.

I was concerned about a voltage differential between the DCS100 Command Station and the boosters, which is why the DCS100 is not connected to the rails. All rail power is via the boosters. Since I'm using 16V power supplies, the voltage at the tracks is around 14.2V which is well within the standard for all DCC systems.

The beauty of DCC is that even though the track voltage is constant, that voltage is only seen by the decoder, not the motor itself. The decoder generally causes about a 2v drop from the track voltage resulting in about 12v to the motor (in my case). Since the motor is controlled by pulse width modulation, limiting the max speed of the motor by CV effectively limits the voltage to the motor. Not an exact science of course.

With respect to the link to Mark Gurries' web page, I don't see the relevance. It simply restates the NMRA standards.
-Joe-

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krokodil
Posts: 675
Joined: Tue Jan 29, 2013 6:46 pm

Re: DIYish DCC Booster Module

Post by krokodil »

"limiting the max speed of the motor by CV effectively limits the voltage to the motor."

Not quite correct ( very often missinterpreted) the CV does not limits any voltage to the motor it limits the power to the motor. This is not the same and can easily damage the motor, when is not designed for the full voltage.
Greetings from Austria
E.T.

sacto-tt
Posts: 224
Joined: Tue Jan 11, 2011 3:23 pm
Location: Sacramento, CA USA

Re: DIYish DCC Booster Module

Post by sacto-tt »

That's why I said "effectively" limits. Obviously with Pulse Width Modulation the full voltage is applied during each pulse, but the lower the throttle setting, the shorter the duration and thus PWM generates an effective voltage based on the cycle. For a slower speed, say 20%, the motor has track voltage (minus decoder drop) applied for 20% of the time and 0v applied 80% of the time. Therefore the effective voltage is .2 x track voltage.

There are "effective" voltage examples on many DCC related pages, such as Mark Gurries' and the DCC Wiki. I would assume that even a low "effective" voltage could damage lower voltage motors (say 6v or lower) but I don't see that as applying in this case.
-Joe-

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krokodil
Posts: 675
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Re: DIYish DCC Booster Module

Post by krokodil »

That is correct, however very often missinterpreted. That is why I am not very happy with such "effective" voltage examples and calculations on many DCC pages. Not in your case, but many people without knowledge in electricity read the standard, what says the DCC booster (etc) can be powered with power packs up to 24V without any mention about the situation in your description. What they do? They power the DCC system with 16 V AC output from the old fashion transformer power packs. This 16 V will create in DCC system about 22-23V DC reduced by losses, it will be 19-20V in the tracks. After the first motor is burned, they read the DCC decoder manual and set the CV to effective 12 V voltage and will very soon discover the next motor damage.... on top of that it is not a simple task to measure the track voltage in DCC system, many DVMs deliver completely different results in the same circuitry.....That is why it is very much recommended to use a switching power pack, like in your case, as these have very exactly defined DC voltage output, there is no discussion.
Greetings from Austria
E.T.

Bill Dixon
Posts: 1363
Joined: Mon Mar 15, 2010 10:57 pm
Location: North Vancouver, B.C.

Re: DIYish DCC Booster Module

Post by Bill Dixon »

krokodil wrote:That is correct, however very often missinterpreted. That is why I am not very happy with such "effective" voltage examples and calculations on many DCC pages. Not in your case, but many people without knowledge in electricity read the standard, what says the DCC booster (etc) can be powered with power packs up to 24V without any mention about the situation in your description. What they do? They power the DCC system with 16 V AC output from the old fashion transformer power packs. This 16 V will create in DCC system about 22-23V DC reduced by losses, it will be 19-20V in the tracks. After the first motor is burned, they read the DCC decoder manual and set the CV to effective 12 V voltage and will very soon discover the next motor damage.... on top of that it is not a simple task to measure the track voltage in DCC system, many DVMs deliver completely different results in the same circuitry.....That is why it is very much recommended to use a switching power pack, like in your case, as these have very exactly defined DC voltage output, there is no discussion.
No.
For example Digitrax boosters have an input voltage range of 13.5 to 20V. After they pass through a bridge rectifier they are regulated to a working voltage. Then there is a user set able track voltage.
So if my booster is set to HO, I get 14.5 V on the track regardless of the booster input voltage.

Lenz systems have a user set able track voltage so it does not matter what the input voltage is, you get the output you choose.
Regards
Bill Dixon
TT-Tracks
North Vancouver, BC

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krokodil
Posts: 675
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Re: DIYish DCC Booster Module

Post by krokodil »

I know, unfortunatelly it is not a general practice. There are still too many boosters without any voltage regulators. Unforunatelly they are the cheapest ones ie most attractive devices for the modellers. There are even systems they show the user on the WAC the track voltage and power consumption of the controlled train. Something like this should be a standard...
That is why I prefer in every case the cheap switched power supplies from computers or general one. There so many on the market, few of them with adjustable output voltage, this is the best what can be used for DCC trains.
Greetings from Austria
E.T.

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