Bachmann Dynamis Without Batteries

[dale159]

Hello,

 

I have a Bachmann Dynamis which I have owned for about 5 years now.

 

I like it as I find it easy to operate and is the only DCC controller I have used that can easily consist my fleet of DMUs without having to reprogram the entire consist when I change ends.

 

I did look at buying an NCE and then ESU ECoS systems, however on trying both of them I found that while I could consist 2 DMUs together and switch off the head and tail lights in the intermediate cabs if I then came to drive the same train in the opposite direction I would have to start the consist again from scratch.

 

So I am happy with my Dynamis as it does what I want it to do very easily, however, as mentioned by numerous people on this and other forums its main drawbacks are its reliance on batteries for the handset, the need to point the handset at the base station to maintain connection and the wireless connection being susceptible to interference from things like strip lights.

 

So that got me thinking - would it be possible to get around these niggles by hard wiring the hand set to the base station taking both an external 6v power supply and bypassing the wireless transmitter and receiver.

 

Does anyone have any experience of dismantling either half of a Dynamis and know wether or not such a thing would be possible? 

 

I have started looking for reasonably priced second hand units but as yet I haven't managed to track one down and I don't really want to got taking my current one apart for fear of not being able to put it back together again.

 

Any help much appreciated.

 

Dale

Edited November 9, 2016 by dale159

[Colin_McLeod]

The two paragraphs about consisting DMUS confused me. Is your question just about connecting the Dynamis to the hand set with a Cable?

[dale159]

The two paragraphs about consisting DMUS confused me. Is your question just about connecting the Dynamis to the hand set with a Cable?

 

Hi Colin.

 

Yes sorry if that's not very clear.

 

The talk of DMUs is just an example of why I prefer the Dynamis and continue to use it. My main question is can you improve it by connecting a cable between the two halves bypassing the Infra-Red and saving lots of AAA batteries.

 

Dale

[Izzy]

Hi Colin.

 

Yes sorry if that's not very clear.

 

The talk of DMUs is just an example of why I prefer the Dynamis and continue to use it. My main question is can you improve it by connecting a cable between the two halves bypassing the Infra-Red and saving lots of AAA batteries.

 

Dale

 

If your concern is mainly with the use of the AAA batteries have you considered using re-chargeable ones? I now use Maplins Hybrid brand and they seem very good as regards power output and length of use/how long they hold a charge. And of course with a separate charger and a couple of sets you can use one set while the other charges. Whether the 4.8v output would be enough for the Dynamis against the 6v of non-rechargeables might be a factor, perhaps someone who knows could advise.

 

Izzy

[dale159]

My initial thought was just for purpose of bypassing the battery usage then I thought if I could do that could I not do the same for the infra-red too.

 

I do own a pack of 4 AAA rechargeables but I've never used them as you said knowing they ate only 1.2v rather than 1.5v the difference may upset the handset.

 

Dale

Edited September 7, 2016 by dale159

[Oakydoke]

With regard to the reliabilty of the infra-red wireless connection between the handset and base station, that can be improved with extra IR receiver/transmitter heads, distributed at appropriate places around the layout.

Of course, you would need to get hold of a ProBox in order to connect these up.

[Colin_McLeod]

To get back to the OP's question: when the covers are removed from the Dynamis and the handset is there an obvious set of terminals that could be connected together with a cable?

Edited September 8, 2016 by Colin_McLeod

[Crosland]

A bit of lateral thinking says just replace the batteries with a wired power supply. The end result is the same, a tethered controller.

 

A better option might be to wire in an external battery holder with C or D cells. A bit of gaffer tape and you still have a wireless, if somewhat heavier, handset. Or put he battery pack on a belt clip with a short cable. The possibilities are almost endless...

[dale159]

Thank you for your replys.

 

I have had time this afternoon to take apart my own Dynamis and see what is inside - It is actually very well made as I had the whole thing apart and re-assembled (and working) in about 15 minutes.

 

First up the base station, just one screw hiding under the Infra-red receiver hold it all together.

Top

 

 

Bottom

 

Then the Infra Red receiver itself

Top

 

Bottom.

 

And finally the Handset.

I couldn't take the board out of the handset for a picture of the other side as the thumb control prevents the board from being moved more than a few mm - must be put on afterwards, don't know if it can be removed.

 

Now my knowledge of PCBs such as this is quite limited so I don't really know what to look for, especially when it comes to the Infra-red side of it. Hopefully it is just a case that the handset converts the control inputs into Infra red where the base station then converts them back again, if there if any amplifying of the signals in between these two then I think it could be a little bit beyond me.

 

Dale

Edited September 8, 2016 by dale159

[Oakydoke]

....Hopefully it is just a case that the handset converts the control inputs into Infra red where the base station then converts them back again.......

Don't forget it works in the opposite direction too.

Communication between the handset and base station is two-way, with the base station sending its own messages to the handset all the time.

[Nile]

You could in theory link the handset and controller with some fibre optic cables. You'd probably need two as the emitters and receivers look to be too far apart. In the photo below I've ringed the emitter LEDs red and the IR receivers green.

 

Has anyone ever tried anything like this?

[dale159]

Hello again,

 

Thank you to everyone who has helped with ideas for my Dynamis.

 

I haven't looked much further into anything as yet, I've been too busy working on my layout - quite rare for me!

 

I have recently acquired a second hand Dynamis Pro box and additional Infra-red receiver, giving a total of 3 including the one from my original Dynamis with scope to add 2 more, so I think that should be the Infra-red signal covered.

 

Back to the handset, I took it apart again and had a poke around with a multi-meter and discovered as follows.

 

I could only get continuity between terminals 2&3.

So I believe 2-3 is a link between the 4 batteries in series and if I were to apply 6v at terminals 1 and 4 as marked on the picture all should be good although I am yet to test this, I also reckon, assuming it all works, I should still be able to use the handset on battery power away from my own layout.

 

My only concern is finding a power supply which isn't going to give too many amps at 6v that is going to damage the innards.

 

I will report back with further updtes

 

Dale

[Nile]

As long as it's regulated it should be ok.

[dale159]

As long as it's regulated it should be ok.

 

I was thinking of using my Gaugemaster controller set to the right voltage with a multi-meter.

 

Dale

[Nile]

Unless it has a pure DC output that's probably not a good idea.

[dale159]

Gaugemaster model P, the track feed from that is variable DC.

 

Dale

[dale159]

I've just taken the plunge and applied power from my Gaugemaster controller to the two terminals on the Dynamis handset PCB I identified previously. Good news is that it does light up as it would on battery power however it did not get passed the boot stage where all the screen icons are illuminated, this only stays on for about a second normally but was still on after 5 or so under Gaugemaster power so I'm not sure what's going on there.

 

Dale

[Phil S]

Do you have a multimeter or voltmeter ? - what was the displayed voltage when used on batteries ?

IF, as seems probable, the circuitry is using '5V logic' (on  a guess) then the battery voltage could probably drop to 4.5V and it should still work.

There are basically 3 ways of protecting the circuitry from reversed battery polarity: 1/ Simple physical battery holder moulding shape.

2/ A series diode - BUT this drops about 0.5-0.7V, which is 'wasted' power - but safely protected circuitry, or 3/ A fused battery supply and a 'wrong direction' diode across the terminals ... so that if it is incorrectly connected, the current takes the 'shirt circuit route' via (the fuse ( and then )  the diode - hopefully casing the battery to blow the fuse instantly before damage can be done elsewhere.

Nowadays there may be more advanced devices which include charge-pump voltage reguation (such as the IC which allows white LEDs to be lit from 1 x 1.2V battery cell)

 

What you need to supply is a smoothed, regulated power supply matching the battery voltage (of 'fresh' batteries) that you have measured.    On Ebay you will find some nicely made, energy efficient 'Step-down' (or even step-up) voltage converters, which will accept your unregulated / unknown / unsmoothed source, and outout the required value  as steady contastant dc.

This is an example from Ebay of a possibly suitable device which includes a Display of the voltage in or out, and current (not in this example):

LM317 AC/DC Adjustable Voltage Regulator Step-down Power Supply Module TY 5S9Z

(look at similar devices with different prices, and read the specifications)

Batteries can provide a surprisingly large current initially - even if not sustainable for long. These modules can output 2A.

(incoming voltage needs to be >3V higher)

 

IF you have a multimeter and connect it to your exisitng supply - and switch its mode to 'AC': then you may get some indication of HOW UNSMOOTH your supply is.... from the ize of the ac voltage measured, compared to what you were expecting.

Restore the meter to dc...

[dale159]

Thank you for your reply.

 

I think I have understood most of it, are you saying that it likely runs on 5v but 6v from the batteries is not enough to harm it.

 

I have multimeter which I used to set the voltage, I chose 6v as this would be equal to the 4 batteries in series. I measured 2 of the batteries (not all that new) both gave a reading of 1.38v

 

Perhaps if I supplied 3v to each pair of positive and negative terminals exactly as through batteries would then it may work, might try that tomorrow.

 

Dale

[Crosland]

There are basically 3 ways of protecting the circuitry from reversed battery polarity: 1/ Simple physical battery holder moulding shape.

2/ A series diode - BUT this drops about 0.5-0.7V, which is 'wasted' power - but safely protected circuitry,

2a/ A MOSFET can be used as a simple polarity protector that drops much less voltage (and thus dissipates much less power) than even a Schottky diode.

 

http://www.ti.com/lit/an/slva139/slva139.pdf

 

Andrew

[Phil S]

Dale replied....

I have multimeter which I used to set the voltage, I chose 6v as this would be equal to the 4 batteries in series. I measured 2 of the batteries (not all that new) both gave a reading of 1.38v

Perhaps if I supplied 3v to each pair of positive and negative terminals exactly as through batteries would then it may work, might try that tomorrow.

 

Phil: I have just scrapped the checks I wrote  because I have zoomed in on the handset photo and spotted on the left side: 4 test terminals (plated through holes?_...

Marked BATTERY(Ubatt)  +      Ub       VCC+       GROUND        I cannot trace links to the right hand batteries form the photo 8-(

There is probably a regulator (unmarked? 3 legs)  located bottom left .... below the Ubatt/Vcc/Grnd terminals.

Connect 4 batteries, as normal: then in VOLTMETER mode measure between [ubatt+]  , [ub],   [VCC+]     and Ground

The VCC +ve positive voltage (compared to Ground=0V) is the power rail for the ICs on board .... you can follow the track across to some ICs to the right.   

 

An alternative power supply replacing the batteries could , in theory, be connected to Ubatt (+) and Ground (-) ... it would then be regulated by the on board regulator to the required voltage.   Try for about 1 V olt more than your measueed VCC+ voltage.

[dale159]

Thank you Phil,

 

I'll need to sit and re-read that on the computer to take it in properly but I think I've got the basics of it.

 

Dale

[dale159]

After a few struggles holding the batteries in with the back removed from the handset, eventually resorting to a pair of G-clamps, I have managed to measure the voltages between the 4 terminals which are as follows.

 

Ubatt-GND is 5.5v and I can measure this even with the handset turned off.

Ub-GND is between 4.50v and 4.56v and can only be measured with the unit on.

VCC-GND is 3.67v

 

I suspect pumping 6v into the battery terminals as I did the other day caused it to enter some sort of surge protection mode (Idiot proofing from people like me!) to prevent PCB parts melting.

 

I have found a surplus power lead from an old radio alarm clock which gives its output as 5.5v at 1 amp, my multi-meter says this is accurate, I'm wondering if this is going to be any use.

 

Dale

Edited November 6, 2016 by dale159

[dale159]

Partial success this evening.

 

First I found a brand new pack of 4 AAA batteries which I measured at 1.62v each on my Multi-meter, I then installed them in the dismantled handset with the assistance of the G-clamps as per yesterday

 

I then measured 6.4v between the Ubatt and GND points and 5.5v between between UB and GND, However still exactly 3.67v from VCC to GND

 

So I powered up the alarm clock transformer mentioned yesterday and wired this between Ubatt and GND and my Dynamis handset fully powered up without batteries, although at only 5.5v this caused the low battery symbol to be displayed on the screen. I then swapped this transformer for my Gaugemaster controller set to 6v but unfortunately this gave the same outcome as the previous time I tried it with all the on screen symbols being displayed when powered up, I imagine this controller is pumping out too many amps for the unit to handle.

 

Dale

[dale159]

I think this might do the job just right set at 6v - https://www.rapidonline.com/powerpax-uk-sw4177-mini-regulated-voltage-adjustable-psu-85-1683

 

Dale