DIY Power buffer

gregh

gregh

electronics, computers and scratchbuilding
A quick question to the electronics boffins out there.

After more extensive trials I have discovered there is still one point on my railway where, even with the buffer, the loco sometimes stalls if I go over it very very slowly. If I wired another 2200uF capacitor in parallel with the original, would I double the duration of the discharge, or would I need to replicate the existing circuit, or what?

Rik
Just wire it in parallel and you'll have double the time. The same limiting resistor will be fine
 
ge_rik

ge_rik

British narrow gauge (esp. Southwold and W&LLR)
24 Oct 2009
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www.riksrailway.blogspot.com
Thanks Greg - it's as I suspected but thought I'd just check.
I've assumed that more or less how Massoth's PowerCap buffer works which gives up to 30 seconds of buffering.


Rik
A quick question to the electronics boffins out there.

After more extensive trials I have discovered there is still one point on my railway where, even with the buffer, the loco sometimes stalls if I go over it very very slowly. If I wired another 2200uF capacitor in parallel with the original, would I double the duration of the discharge, or would I need to replicate the existing circuit, or what?

Rik
Just wire it in parallel and you'll have double the time. The same limiting resistor will be fine
 
ge_rik

ge_rik

British narrow gauge (esp. Southwold and W&LLR)
24 Oct 2009
9,707
292
Cheshire
www.riksrailway.blogspot.com
Struggled to find sufficient space inside my Fowler diesel for the capacitor so 'borrowed' an idea from the guy who wrote the original article in Voie Libre. He mounted two capacitors on the bonnet of his diesel to represent air tanks - so why not an air tank on the footplate of my model?



Will blend it in more when I weather the loco.

Rik
 
beavercreek

beavercreek

Travel, Art, Theatre, Music, Photography, Trains
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Great thread and excellent ideas and tips.
The air tank idea is definitely one to use. Even if, and I am definitely not saying anything against your little beauty of a loco Rik, it was too short for a prototypical appearance on another type of diesel/steamer, it or they could be mounted inside a cylinder(s) of the correct dimensions. For narrower air tanks (like on the sides of steam locos) multiple caps of a lower value could be wired in parallel and inserted into the 'air tank' tube like a row of batteries.
Of course large locos would not need this 'external' device.
 
ge_rik

ge_rik

British narrow gauge (esp. Southwold and W&LLR)
24 Oct 2009
9,707
292
Cheshire
www.riksrailway.blogspot.com
Great work, Paul and a really convincing video!
Only too glad to spread the word - like all good things, the idea was 'borrowed' from others and implementation guided by those with far more knowledge than me.

Rik
 
Zerogee

Zerogee

Clencher's Bogleman
25 Oct 2009
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North Essex
Having read back through this whole thread, I can't find an answer to one question - why is the capacitor shown as a MAXIMUM of 2200uF, but it is possible to use two (or more?) in parallel? Is there a simple reason why a single capacitor of a larger size can't be used?
Thanks!

Jon.
 
beavercreek

beavercreek

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Hi Jon
It is probably to do with size or/and price. Also perhaps there is a difference in charging time with two 2200 as opposed to a 3500 etc.
 
ge_rik

ge_rik

British narrow gauge (esp. Southwold and W&LLR)
24 Oct 2009
9,707
292
Cheshire
www.riksrailway.blogspot.com
Having read back through this whole thread, I can't find an answer to one question - why is the capacitor shown as a MAXIMUM of 2200uF, but it is possible to use two (or more?) in parallel? Is there a simple reason why a single capacitor of a larger size can't be used?
Thanks!
Jon.
Jon
According to the German techie guy on the original Massoth forum posting

Elektrolyt condenser:
- The capacity should not be higher than 2200µF, while charging takes too long.
- In place of 1 big Elko you can also use more smaller Elkos parallel.

which seems to imply that a larger capacitor can be used but the charging time would increase. I assume that if the loco encounters a series of dead spots in rapid succession then a larger capacitor would not not have time to charge up between them. Putting several 2200uF (or smaller) in parallel would increase the discharge time to take the loco over longer dead spots.

I'm sure someone with more technical knowledge than me will be able to correct or elaborate

Rik
 
Zerogee

Zerogee

Clencher's Bogleman
25 Oct 2009
16,805
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North Essex
Thanks Rik - that explanation certainly makes sense. :clap:

Jon.
 
whatlep

whatlep

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I'm a convert to power buffers.

Once fitted the prospect of small locos stalling on points is gone.
It's a small point but important for maintaining the smooth running of a railway.
Good aren't they? All my 4-wheel locos have had them installed this year and they run beautifully whatever the track conditions.
 
trammayo

trammayo

Interested in vintage commercial vehicle, trams, t
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Could capacitors be fitted to analogue locos? And, if so, what would happen in the case of needing to do an emergency stop - would it continue far?
 
Zerogee

Zerogee

Clencher's Bogleman
25 Oct 2009
16,805
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North Essex
I'm not sure of the answer to Mick's query, I would think they would trundle on till the capacitors go flat!

Following on from that question, but back to DCC....
Does the emergency stop function on most DCC systems work by sending a "STOP NOW!!" command to all locos on the track, or simply by cutting all power to the track? If the former, then even locos with buffers should stop immediately - but if the latter, then those with buffers may well carry on for a couple of seconds at least, which COULD be a problem in certain circumstances......

Jon.
 
dutchelm

dutchelm

Registered
24 Oct 2009
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I think there might be a problem with polarity on analogue locos. Put it in reverse and the capacitor goes bang.
 
B

bunnyrabbit03

Registered
24 Oct 2009
456
0
Wiltshire
An interesting thread. I am amazed that you are all experiencing such a difference in running characteristics with such a small capacitor. I use 10000mF in my locos, which improves slow running very occasionally for single motor lcoos, but I mainly use it to make the sound less perceptible to occasional power interruptions due to dirty track.

I think I mentioned this before, but Zimo decoders (I use both Large Scale and HO decoders) allow you to connect capacitors directly to the decoders without the need for any other components. They also allow you to programme the decoders with the capacitors connected, so there is no need to install a switch or similar. Also, the new ESU Loksound and Lokpilot 4.0. XL and the old ESU Lokpilot 3.5 XL all have gold caps built in, so there is no need for capacitors.
 
B

bunnyrabbit03

Registered
24 Oct 2009
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0
Wiltshire
I'm not sure of the answer to Mick's query, I would think they would trundle on till the capacitors go flat!

Following on from that question, but back to DCC....
Does the emergency stop function on most DCC systems work by sending a "STOP NOW!!" command to all locos on the track, or simply by cutting all power to the track? If the former, then even locos with buffers should stop immediately - but if the latter, then those with buffers may well carry on for a couple of seconds at least, which COULD be a problem in certain circumstances......

Jon.
Hi Jon,

As far as I know, the emergency stop button on DCC cuts the power to the track with the result that the power buffer would power your loco, which might cause problems in certain circumstances. However, with a small capacitor, this is very unlikely to happen. With the Massoth gold caps (not the now discontinued large single capacitor), however, this is a real possibility.

I am using the Lenz DCC system and with this I can configure the emergency stop button so that the system sends a stop signal to all locos but does not cut the power to the track.
 
Zerogee

Zerogee

Clencher's Bogleman
25 Oct 2009
16,805
202
North Essex
.............
I am using the Lenz DCC system and with this I can configure the emergency stop button so that the system sends a stop signal to all locos but does not cut the power to the track.
Thanks Bunny - I believe that my Massoth can be configured the same way (I think the two STOP buttons can be programmed so that one does each type of "stop"), I'll have to double-check the manual and figure out exactly how - but I just wondered about other systems like MTS....?

I just thought it was a point worth considering by anyone who is installing buffers in several locos, whether DIY or commercial types.

Jon.
 
PhilP

PhilP

G Scale, 7/8th's, Electronics
5 Jun 2013
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Another 'problem' (or is it a 'feature') as that if a loco derails, then the motor will keep turning until the buffer runs down. - Can be a problem with the motion chewing-up scenery / damaging itself.

My suggestion is to limit the size of buffer to a minimum. - If you have a *really* dodgy section, or point, sort out the source of the problem. It will only get worse.
 
ge_rik

ge_rik

British narrow gauge (esp. Southwold and W&LLR)
24 Oct 2009
9,707
292
Cheshire
www.riksrailway.blogspot.com
Could capacitors be fitted to analogue locos?
Hi Mick
See Greg's post #18 on this thread re a circuit for analogue locos - http://www.gscalecentral.net/fb.ashx?m=277663 < Link To http://www.forum.gscalece.ral.net/fb.ashx?m=277663

And, if so, what would happen in the case of needing to do an emergency stop - would it continue far?
The capacitors used in these DIY circuits give little more that 0.5 seconds of current - enough to take the loco over short dead-spots but not enough to keep them running on uncontrollably. With the Massoth units you can get up to 30 seconds of running after loss of track power but they require a bank of capacitors to be installed somewhere in the loco.

Rik
 
trammayo

trammayo

Interested in vintage commercial vehicle, trams, t
24 Oct 2009
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Thanks Rik - and everybody that commented - I'll look at the link. I'd never thought about the reversing! It just seemed a possible solution to stalling on points (trailer layout).

I.m clutching at straws in a way I suppose. I'll have to sort things out after the last show of the year (for me anyway!).

JUst looked at Greg's post - I think that I'll run that past my brother if I don't sort it out.
 
Zerogee

Zerogee

Clencher's Bogleman
25 Oct 2009
16,805
202
North Essex
Thanks Paul, very useful to know! :clap:

After taking today's mailings to the Post Office, I circled round and nipped in to the Rapid trade counter (very handy having it so close, and open till 6pm!); for less than a tenner all-in, I picked up enough 2200uF caps, 1 watt resistors and 1N4007 diodes to make up to twenty buffer units! Mind you, at my rate of doing things they'll probably sit there for a year before I get round to making any of them up..... ;)

Jon.