Tantalum Capacitors

[bigal10]

I've recently been experimenting with storage capacitors attached to my Zimo sound decoders. (my fleet of about 16 locos has nearly all Zimo, except for some pre-installed Loksound in off-the-shelf Bachmann jobbies.

 

I read in the Zimo Kleine-decoder manual, and the 'Zimo.at' website that they offer "Tantal Packs" for storage, indicating that they are physically smaller than Radial Electrolytic Caps, which plainly they are!

 

Like most decoder websites these days, they are pleased to announce well in advance of actual delivery that items and features are available,

(oh!, and on a similar subject when can we expect the ADAPMTC ? - which I would dearly love to trial, if only to save my poor old eyes when it comes to the impossible task of soldering wires to 'solder tabs' on a decoder)

 

Has anyone any experience of using tantalum capacitors for storage in this way, the obvious difference in physical size seems very appealing, but trawling through a few supplier's websites, (Rapid / Conrad) only seems to show the largest at 1uf at 25v, whereas the Zimo manual/website has a photo purporting to be 50000uf 25v 'pack'

 

I have managed to stuff one 4200uf 25v Electrolytic inside my lovely new Dapol 52, and at a pinch 2 x 2200uf 25v side-by-side, but I must confess i'm confused what the actual effects are.

- testing the Dapol 52 with either of the above, by switching the ECoS off via the red button, you can see an obvious change in the lighting, ie: at 220uf almost instant lights-out, with 4200uf the lights last about 2 seconds, then fade. With the loco moving, there seems to be no motor run-on when 'pulling the plug' via the red button, I have yet to try a full run around my layout hunting for dirty track, (I know that we should have spotlessly clean track and wheels everywhere, and stay-alive is no substitute, but hey, everyone has a dodgy frog or two, don't they?)

 

Any info gratefully received,

 

Regards,

 

Alan Richards

[Nigelcliffe]

I've probably experimented a little further than you.  The two most recent items in my blog are on the topic:

 

www.nigelcliffe.blogspot.co.uk

 

I've also written a long article which will be in Scalefour News sometime this winter. 

 

I've not used Tantalum's, instead used some ceramic capacitors which are even smaller.  

There are a handful of 16v 220uF Tantalum's in the Farnell UK catalogue, and there may be some 330uF examples.

 

I think the Zimo website might be ambiguous, I took their tantalum pack to be 16v rated, not 25v.  

16v is fine with most control systems, though dangerously marginal with the Roco Multimaus and Bachmann EZ.

 

 

The effect of a few thousand uF of capacitors is small and subtle (5000uF = 0.005 F).  You're looking at a run time of a loco in the region of 0.1 to 0.3 seconds.  That's enough to stop "stuttering" on small specs of dirt, and will stop audio interference on sound chips, lamps flickering, etc..  But it doesn't run a loco over dodgy track !  

 

If you want to run for more than this, you need much more energy, something approaching 0.1F.   Gold-caps (or super-caps) are a solution, and the quickest/cheapest off the shelf option is to fit a TCS KA1 or KA2 to a Zimo chip - wire the TCS unit directly onto the decoder positive and decoder negative, not the "capacitor charging contacts" fitted to some Zimo decoders.  The TCS units have the charge/discharge circuits within them (so don't need extra diodes/resistors for charging), though the TCS don't have the inductor which means loading new audio is going to require disconnecting the stay-alive.  Normal CV programming is OK with the stay-alive connected.  

A KA1 will give you around 6 seconds of running, the KA2 nearer 20 to 30 seconds.  There is an optional argument that you should fit a discharge resistor across the positive/negative wires, something around 2kOhm as a suggested starting value.    I've used both TCS units on various Zimo chips, usually sound ones which I've been fitting in other people's models. 

 

 

- Nigel

[Crosland]

The Rapid website shows plenty of tantalums larger than 1uf, even at 25V. I would go for the surface mount types as they are a regular shape that may ease building up a "pack".

 

As Nigel says, ceramic capacitors have advanced considerably in recent years. You can get, e.g., 22uF/16V in a 1206 case (3.2 x 1.6 x 0.5mm) at 16p ea from Farnell.

 

Andrew

[dave flint]

Having been very disappointed by some stay alive fitted decoders in the past I'm tempted by tbe tcs ka1 and ka2.

 

Nigel, you mention the ez commamd as chucking out more than 16v. I have one which my son finds easy to use. now.....I recall a post on here or another forum where someone mmentioned the ka1 was a bit marginal above 16v as well.

 

Is this true or can it be uaed with an ez command - I don't want to fry any.

[Nigelcliffe]

I'm pretty certain the TCS documentation says 16v track voltage maximum.  I've taken a KA2 apart, and I think its just OK at 16v, and any more requires going over the specification of the components. They may stand it, but you're outside specification.

 

Some years ago, a friend and me measured a Bachmann EZ at around 19-20v on the track with the standard Bachmann power supply.  With a much lower 11v AC supply, the EZ put out what we thought was a sensible track voltage for N/2mm models.   

 

Personally I wouldn't use the EZ with a TCS KA1/KA2.

 

- Nigel