Zimo MX645R and stay alive capacitors

[Roger Sunderland]

Just checking on this please. The 645 has internal circuitry to limit the output so it can be used with 16V capacitors. However, I have a 25V , 1000uf, electrolyte capacitor- is it ok to use this with the MX645?

[Nigelcliffe]

Yes, its safe. 

 

But its a huge waste of space in that a 16v electrolytic of 1000uF will be much smaller, and only costs pence.  And other capacitor technologies will give a much greater run time for your £100 decoder.  

 

I've just fitted a couple of the £15 stay-alive modules from Digitrains into two Bachmann J72's.  The locos now run about 18 inches without power (comically ran them down a section of the layout which hasn't got the rails laid yet).  So now need the run-time before stopping CV turning down in the decoders.   

 

 

[Roger Sunderland]

Thanks Nigel, yes I thought that would be the case. Space isn’t really an issue in this case but I know that 1000uf won’t give me a massive amount of run time.

In the same vein I also have a You Choos 17000uf super capacitor rated at 15V which I’m assuming would also be ok with a 645. If so I’m thinking this would give me about 5 minutes run time!!!

Edited August 12, 2021 by Roger Sunderland
Mistake

[Nigelcliffe]

17,000uF won't give you 5 minutes of run time.  Possibly seconds.  

I've not checked the capacitance of the units I fitted today, but assume they're above 100,000uF.    

 

Fitting the 17,000uF device puts you in a tricky place.   Following Zimo's manual, the Zimo decoder's charging circuit isn't rated to handle that much energy storage (max of 5000uF, with 6800uF permitted).  But, my understanding of charging physics can't put any explanation on the figure Zimo set (a smaller capacitor charging/discharging more frequently is the same current flowing through resistance of the charging circuit as a larger capacitor charging/discharging less frequently, so same heating effect, same detrimental effect (if any) on the rest of the components).   

Up to you if you choose to break Zimo's recommended limit.    

 

The alternative is to ignore the Zimo internal circuitry, and connect to the decoder positive and decoder negative, using your own charge/discharge circuitry.  

 

 

 

- Nigel

 

 

 

 

[Izzy]

11 hours ago, Nigelcliffe said:

 So now need the run-time before stopping CV turning down in the decoders.   

 

 

What is this cv please Nigel? Being my usual self I can’t find mention of it in the manual, perhaps I am not looking in the right section. 
 

Bob

Edited August 13, 2021 by Izzy

[Nigelcliffe]

10 hours ago, Izzy said:

What is this cv please Nigel? Being my usual self I can’t find mention of it in the manual, perhaps I am not looking in the right section. 
 

Bob

 

Zimo run-time without DCC signal is CV153.   Value in tenths of second, so 10=1second.  250=25seconds.  

[Izzy]

50 minutes ago, Nigelcliffe said:

 

Zimo run-time without DCC signal is CV153.   Value in tenths of second, so 10=1second.  250=25seconds.  

Many thanks Nigel.

[Roger Sunderland]

Yes many thanks for your help Nigel.