3 aspect model RR signalling help plse

[angie1199]

HAPPY CHRISTMAS MrDEB AND PETE

 

[MrDEB]

MERRY Christmas to all on Electro-tech

 

[MrDEB]

twin t revision

here is the circuit you have built.
can't figure out how you get a dim LED.
I changed the track resistor from 10 - 10k
I get very little current draw at am3.
what LEDs and how much voltage do you have at VF2 with and without loco?

 

[Raiway Pete]

here is the circuit you have built.
can't figure out how you get a dim LED.
I changed the track resistor from 10 - 10k
I get very little current draw at am3.
what LEDs and how much voltage do you have at VF2 with and without loco?

MrDeb Angie. I have about 900 Ohms in T4s collector circuit and an LED. Also the cap C3 is too small. 47 to 100 yF works well.

Vcc = 11.5
T4 collector no detect = 10.5
T4 collector detect = 0.05

C3 = 100yF or 47yF.

During no-detect that means I have about 1 volt across the LED and the 900 Ohms. that's not enough current (1.6 Ma) to turn it on. Track resistance make no difference.

Locos.
Angie are you just putting two locos on a test track and having them stand there or are you actually running them. The decoders in quiescent state have high resistance, and its the decoders that contrll the motors.

Also have you measured your relay coil resistance yet. If they are 12 volts and have a coil resistance of over 650 ohms they should work. In the mean time put a 1K resistor in series with the LED. 550 Ohms is a little low and you are exceeding the upper 20Ma limit just a bit.

 

[MrDEB]

TINA sim is close to actual

at T4 collector
no detect = 82.6mv
detect = 11.91
using 550 for LED resistor as the meter AM3 shows 18.77ma
with 1k = 10.39ma
on the relays, most 12v relays I have seen are 400 ohm.
thinking a reed relay might be better?
need to research cost of 12v relays vers 5v relays
could be different?
also reed vers coil relays.
I wonder about a resetable fuse in case of derailment?

 

[MrDEB]

link to a relay from Rapid
Rapid Electronics - Electronic Components
320 ohm col@38ma
contacts 2A (forgot already?/)

 

[MrDEB]

We have a winner!

using Petes revised circuit and the signal circuit that started this thread we , pretty sure, have a winner.
using the small relays (see link I posted) for 320 ohm relays.

 

[Raiway Pete]

at T4 collector
no detect = 82.6mv
detect = 11.91
using 550 for LED resistor as the meter AM3 shows 18.77ma
with 1k = 10.39ma
on the relays, most 12v relays I have seen are 400 ohm.
thinking a reed relay might be better?
need to research cost of 12v relays vers 5v relays
could be different?
also reed vers coil relays.
I wonder about a resetable fuse in case of derailment?

Seems to be OK. Reed relays usually are a lot cheaper as they are nothing but a reed switch wrapped in a coill. They're also designed for low current operation.

Resetable circuit breakers are available for DCC. They are super fast and also super expensive. However the track is protected but the trackside accruments with their own power supply should have something simple as a safety device.

Angie,
I don't think there is any place on your layoout that will need 16 amps at 230 volts AC, But try the 400 ohm coils. I think the 2N3904 can deliver OK. If that works your problem is solved for a few blocks anyway.

 

[MrDEB]

n channel mosfet?

I tried to sim using 500 ohm relay coil - won't switch on.
got to wondering if maybe a mosfet would have less internal resistance thus taking the signal detect switch to zero ground.
Seeing how a NPN transistor won't do the deed. A relay with very little coil resistance(seems like anything over 350 ohms won't switch on.
would a n chammel mosfet do the deed?
tried a 2n6755 in Tina sim and it worked but that mosfet is for lots of current.
never worked with mosfets but mat be an alternative to using relay?

 

[Raiway Pete]

I tried to sim using 500 ohm relay coil - won't switch on.
got to wondering if maybe a mosfet would have less internal resistance thus taking the signal detect switch to zero ground.
Seeing how a NPN transistor won't do the deed. A relay with very little coil resistance(seems like anything over 350 ohms won't switch on.
would a n chammel mosfet do the deed?
tried a 2n6755 in Tina sim and it worked but that mosfet is for lots of current.
never worked with mosfets but mat be an alternative to using relay?

MrDeb,

Are you sure the 500 Ohm relay coil was a 12 volt relay. The voltage swing I have here is from 0.5 volts to about 11. If it's a 12 volt relay it should latch. The 3906 should be able to handle 25 Ma or so easily.

PS

I also strongly sugwest that you put a diode across the relay couils to prevent back EMF from damaging the driver transistor.

P.

P.

 

[MrDEB]

yes on the diode.
I am just inserting different componet to see what works.
pretty sure its a 12v relay.
not sure if I can designate voltage?
will check back

 

[MrDEB]

relay parmeters

no voltage designation?

 

[mneary]

35mA in 100 ohms is 3.5V. It's a "5V" relay.

 

[angie1199]

here is the circuit you have built.
can't figure out how you get a dim LED.
I changed the track resistor from 10 - 10k
I get very little current draw at am3.
what LEDs and how much voltage do you have at VF2 with and without loco?

Ok guys, here we go.

As I said I didn't think I had a capacitor, but now I have a 105 capacitor stripped from the microwave circuit board.

With this from MrDEB, https://www.electro-tech-online.com/attachments/twn-t-revision4-png.36676/

Loco1 activates this circuit brilliantly, stationary or moving.

However loco2 still has greens lit when on the block. When stationary the greens are as bright as red and yellow. When moving, greens dim more but still fairly bright.

Loco2 obviously uses different amount of current.

If I put a 1K resistor across the tracks while Loco2 is on the block, signalling works fine but the signals remain active if the 1K resistor is there when Loco2 is removed.

So would I need a higher or lower resistance across the track to make it more sensitive or should I put a resistor in Loco2 between the wheel and decoder pickup?

VF2 = 9.55V

 

[angie1199]

With LOCO1 VF2 = 9.15V

With Loco2 VF2 = 9.55V

No Loco VF2 = 10.6V

 

[angie1199]

Yay!!!!!!!!!!! We have victory.

Added two signal diodes to green ground on each block.

Changed resistor R8 to 2.2K.

Works great with both locos and dry finger across rails.

Tried 10R resistor across rails. Worked but smoked

Have no idea what I was doing but it works. Now need to find out what power each wagons axle resistor has to be so it doesn't burn out and that's something else I don't know how to do.

 

[Raiway Pete]

Yay!!!!!!!!!!! We have victory.

Added two signal diodes to green ground on each block.

Changed resistor R8 to 2.2K.

Works great with both locos and dry finger across rails.

Tried 10R resistor across rails. Worked but smoked

Have no idea what I was doing but it works. Now need to find out what power each wagons axle resistor has to be so it doesn't burn out and that's something else I don't know how to do.

Hi Angie,

Glad you have success. The two diodes in the emiters lifted them up to meet the cut off level at their bases.

To get the axle resistor value (1 per car, I guess) Put 10K across the track. If it works increase the resistance until it the circuit stops detecting. Reduce the value by 10% to give you some slop. That is the value that each car has to supply across the track.

To calculate the wattage use this. V²/R . If your DCC is 16 volts and your max resistance is 10K ohms V²/R = 16v×16v / 10000ohms. =1/40 watt

If the max resistance is 1K then V²/R would be ¼ watt.

I would also increase the signal LED resistances to 680 ohms. At 470 ohms you are putting about 24 Ma through each LED. That is 20% higher than the max rating of most LEDs. 680 ohms will reduce the current to about 15 Ma. That won't dim the LEDs much. My signal LEDS have a max rating of 20Ma. I run them at 7Ma with excellent results.

P.

Pete

 

[MrDEB]

R8 is the yellow LED resistor. At 2.3K how does it even light? unless we are talking about two different resistors.
my last post I failed o change the relay coil resistance. the posted pic was the default relay. sorry for false posting.
glad to hear you got it working.
post a finalized schematic. Oh yea we still have the relay issue to deal with.
look at the reed relay I linked to from Rapid electronics.
The 5v = .62p and the 12v are .72p
you could go with either one as the max voltage is really a wide swing.

 

[MrDEB]

**broken link removed**

**broken link removed**

 

[angie1199]

To get the axle resistor value (1 per car, I guess) Put 10K across the track. If it works increase the resistance until it the circuit stops detecting. Reduce the value by 10% to give you some slop. That is the value that each car has to supply across the track.

To calculate the wattage use this. V²/R . If your DCC is 16 volts and your max resistance is 10K ohms V²/R = 16v×16v / 10000ohms. =1/40 watt

If the max resistance is 1K then V²/R would be ¼ watt.

I would also increase the signal LED resistances to 680 ohms. At 470 ohms you are putting about 24 Ma through each LED. That is 20% higher than the max rating of most LEDs. 680 ohms will reduce the current to about 15 Ma. That won't dim the LEDs much. My signal LEDS have a max rating of 20Ma. I run them at 7Ma with excellent results.

Ok here we go.
Maximum resistor across track = 470K
Less 10% = 423000R
V x V = 256
(V * V) / R = very tiny, so tiny my calculator can't work it out.

Sound about right? Most resistors I have are 0.6 Watt.

I've increased LED resistors to 628R and yes, they didn't reduce in brightness noticeably. They are 2V - 2.2V (max 2.5V) with max current of 25mA, typical of 20mA.