Lighting Trains

[gavino200]

I think this is the way to go. I'll start searching voltage regulators. What would be great would be a printed strip similar to the popondetta strip. Except without the switch and with pads for wires instead of the 'Kato type" contact legs. It's very simple to solder components onto a board like that, and it should be a 'one size fits all" solution.

Edited February 27, 2019 by gavino200

[chadbag]

I don't know anything about voltage regulators but here is one with input between 7-35V and output of 5V

 

https://www.mouser.com/ProductDetail/STMicroelectronics/L7805ACV?qs=xv3lWMc77RdYd2PeLwOwYw%3D%3D&gclid=EAIaIQobChMI29XXsqTc4AIVCyCtBh0i2wUbEAQYASABEgKacvD_BwE

 

 

Probably something like that?

 

[Sheffie]

I don’t think you need a voltage regulator necessarily. That’s an important component if you need to handle a supply that’s unpredictable, but if all you need is to reduce, say, 9V to 5V then you can use a potential divider to get the same effect. 

[chadbag]

5 minutes ago, Sheffie said:

I don’t think you need a voltage regulator necessarily. That’s an important component if you need to handle a supply that’s unpredictable, but if all you need is to reduce, say, 9V to 5V then you can use a potential divider to get the same effect. 

 

But the regulator would be good since people run trains at different voltages and this would get you to a known voltage no matter what your power supply was feeding.

 

[cteno4]

Yes voltage reg is for dc operation mainly here I think. That’s what I was look at it for. Led strips are 12v so only for dcc

 

jeff

[chadbag]

10 minutes ago, cteno4 said:

Yes voltage reg is for dc operation mainly here I think. That’s what I was look at it for. Led strips are 12v so only for dcc

 

 

You'd have to use 5V LED strips with the regulator, and use a rectifier bridge to convert the DCC style voltage to DC

[gavino200]

41 minutes ago, Sheffie said:

I don’t think you need a voltage regulator necessarily. That’s an important component if you need to handle a supply that’s unpredictable, but if all you need is to reduce, say, 9V to 5V then you can use a potential divider to get the same effect. 

 

Please tell more about potential dividers.

[gavino200]

23 minutes ago, chadbag said:

 

 

You'd have to use 5V LED strips with the regulator, and use a rectifier bridge to convert the DCC style voltage to DC

 

This is true. If the rectifier stays then we're talking about DC.

[chadbag]

How does something like this work?  Are these strips with different resisters etc to work at 5V?  or do they up the 5V USB to 12V and drive the same sort of 12V strips?  I don't see a transformer but maybe for that it would be small and inside the end?

 

https://www.ebay.com/itm/US-5V-50CM-1M-5M-USB-Cable-Power-LED-Strip-Light-Tape-Warm-White-RGB-Background/323282737681?hash=item4b45271a11:m:mcgG7YCUQr6U-jFcwZ54Nig:rk:83:pf:0

 

[gavino200]

12 minutes ago, chadbag said:

How does something like this work?  Are these strips with different resisters etc to work at 5V?  or do they up the 5V USB to 12V and drive the same sort of 12V strips?  I don't see a transformer but maybe for that it would be small and inside the end?

 

https://www.ebay.com/itm/US-5V-50CM-1M-5M-USB-Cable-Power-LED-Strip-Light-Tape-Warm-White-RGB-Background/323282737681?hash=item4b45271a11:m:mcgG7YCUQr6U-jFcwZ54Nig:rk:83:pf:0

 

 

In that case a resistor is all that's need ed to reduce the current to where it won't blow the LEDs.

 

In the case of the Caps it's more complicated as the voltage needs to be reduced. After that less resistance or possibly no resistance would be needed to reduced the current to where it won't blow the LEDs. 

 

 

[Sheffie]

2 minutes ago, gavino200 said:

 

Please tell more about potential dividers.

Okay, simplified example. You have a 9V battery, a 3V bulb, and three resistors of equal value. 

 

If you wire up the resistors in series with the battery, the voltage will drop from 9V to zero across the three of them. Put a multimeter across any one and it will read 3V. Put in across two of them, and it will read 6V. The fraction of the total voltage you see is equal to the fraction of the total resistance. 

 

So, you can wire wire up the bulb in parallel with any one of the resistors and it will get 3V. (This assumes the resistance of the bulb is large compared to the other resistors. If it isn’t, the calculations become a bit more complicated, and the voltage will be less than 3V by some amount.)

 

This basic pattern—connect the power supply across two or more resistors (or a variable resistor) and wire your component across just one, to get a fraction of the total voltage... is called a potential divider (before Alessandro Volta, voltage was called “potential”). 

[chadbag]

3 minutes ago, gavino200 said:

 

In that case a resistor is all that's need ed to reduce the current to where it won't blow the LEDs.

 

In the case of the Caps it's more complicated as the voltage needs to be reduced. After that less resistance or possibly no resistance would be needed to reduced the current to where it won't blow the LEDs. 

 

 

 

What I was alluding to, is that if you use a voltage regulator to get down to 5V, you need a string of LEDs that have the "correct" resistors to work with a 5V input.

 

[gavino200]

4 minutes ago, Sheffie said:

Okay, simplified example. You have a 9V battery, a 3V bulb, and three resistors of equal value. 

 

If you wire up the resistors in series with the battery, the voltage will drop from 9V to zero across the three of them. Put a multimeter across any one and it will read 3V. Put in across two of them, and it will read 6V. The fraction of the total voltage you see is equal to the fraction of the total resistance. 

 

So, you can wire wire up the bulb in parallel with any one of the resistors and it will get 3V. (This assumes the resistance of the bulb is large compared to the other resistors. If it isn’t, the calculations become a bit more complicated, and the voltage will be less than 3V by some amount.)

 

This basic pattern—connect the power supply across two or more resistors (or a variable resistor) and wire your component across just one, to get a fraction of the total voltage... is called a potential divider (before Alessandro Volta, voltage was called “potential”). 

 

How small can this setup be? What do you think Popondetta is using?

[gavino200]

1 minute ago, chadbag said:

 

What I was alluding to, is that if you use a voltage regulator to get down to 5V, you need a string of LEDs that have the "correct" resistors to work with a 5V input.

 

 

Yes. In this case we'd have to use trial and error (again - Dani did it for us the first time) to find a resistor that's perfect.

[chadbag]

1 minute ago, gavino200 said:

 

Yes. In this case we'd have to use trial and error (again - Dani did it for us the first time) to find a resistor that's perfect.

 

It is not just our resistor, but the resistor in the strip on each LED

[gavino200]

3 minutes ago, chadbag said:

 

It is not just our resistor, but the resistor in the strip on each LED

 

It's the sum of both of them. Likely these LEDs would still be too bright at a lower voltage and need extra resistance. 

 

But yes, if that turned out not to be the case, the inbuilt resistors would need to be replaced. That's theoretically possible.

 

I think the most likely solution would be to print a board with a parallel ladder configuration with pads to add the LEDs ourselves (which would be very easy). Basically to print a  simplified version of the Popondeta board.

[chadbag]

Yeah but being able to use LED strips would be nice.  ONce you start making PCB and buying all the parts etc you may get up to the price of the popondetta or similar.

 

[gavino200]

1 hour ago, chadbag said:

Yeah but being able to use LED strips would be nice.  ONce you start making PCB and buying all the parts etc you may get up to the price of the popondetta or similar.

 

 

Agree. It would be nice. But those caps take up a lot of space.

 

How much did it cost to make those little decoder Adapter boards you made? What was the process like? Who designed the board?

[chadbag]

At the "sample" quantity I got, they were about $2 a piece.  I don't know what they would be in more volume.  I also don't know if there are parameters of this potential project you are "proposing" that would make them less or more expensive.

 

The guy who made the files for the decoder board is listed in that topic (start at the back).

[gavino200]

4 hours ago, chadbag said:

At the "sample" quantity I got, they were about $2 a piece.  I don't know what they would be in more volume.  I also don't know if there are parameters of this potential project you are "proposing" that would make them less or more expensive.

 

The guy who made the files for the decoder board is listed in that topic (start at the back).

 

Thanks Chad. I'll check into if it turns out to be necessary. But only after I've got a working prototype and know exactly what setup is optimal.

[chadbag]

I just ordered a clone of that 5V voltage regulator 3 prong chip to test with.  And a 5V LED strip.  We'll see what I can come up with once it gets here.

[gavino200]

I had assumed that the black component on the left in the Popondetta board was a six pin chip of some sort seen from one side....

 

https://popondetta.com/maker/?p=242

 

....but could it be that this is a three pin voltage regulator seen of the type posted by Chad. Jeff may have answered this question earlier, but I had assumed he was reasoning deductively rather than recognizing a component by sight.

 

https://www.mouser.com/ProductDetail/STMicroelectronics/L7805ACV?qs=xv3lWMc77RdYd2PeLwOwYw%3D%3D&gclid=EAIaIQobChMI29XXsqTc4AIVCyCtBh0i2wUbEAQYASABEgKacvD_BwE

 

 

A few questions:

 

Can anyone suggest what might be an "ideal/suitable" voltage for the downstream LED/Capacitor circuit?

 

Can anyone guess what the two small black components upstream of the presumed voltage regulator in the Popondetta setup are?

 

Is there a rectifier in the popondetta setup?

 

Could the chip be a combined rectifier/voltage regulator?

Edited February 28, 2019 by gavino200

[gavino200]

12 minutes ago, chadbag said:

I just ordered a clone of that 5V voltage regulator 3 prong chip to test with.  And a 5V LED strip.  We'll see what I can come up with once it gets here.

 

Do you have a link to the store? I get it, you wan to use a pre-made LED strip. I'd like to use Pre-made strips too, but I'm not married to it yet. 

 

I usually use a 5V supply with LEDs. It's still massively in excess of the what we need to run LEDs at modelling brightness. 5V gets you into the range where you can use ceramic smd caps - but only just.

 

I wonder if it would be possible to take the voltage down further. A calibrated variable voltage power supply would be handy for working this out. 

[chadbag]

I just found some on Aliexpress.

 

[chadbag]

I also bought some 10V ceramic 100uF caps and some 10V 220uF tantalum.  And a bunch of 0805 and 1206 size LEDs in white and yellow (hopefully equal to warm incandescent look).  These are individual non-right-angle smd LEDs in case I make my own strips.

 

ETA:  and some SMD zener diodes 5.1V or something like that.

Edited February 28, 2019 by chadbag