Time clock - triggering multiple lights

Thread Starter

BJS171047

Joined Sep 18, 2019
6
I have a model railroad and wanting to simulate day and night, have lights in buildings turn on and off at the appropriate time, I purchased an electronic clock system from a company in the US. This was about 8 years ago and the company is no longer in existence.
The clock is a fast clock where the ratios can be altered so that 24 hours can be speeded up to be in an hour, 2 hours, 3 hours etc as required.
The system is 12v and has 14 outputs from which lights in buildings can be connected.
Each output has pre-determined on / off times, all of which are unique from each other. The purpose being that the building lights will go on and off at different times during the night times as triggered by the clock throughout a 24 hour cycle. In other words, individual building lights are triggered on and off accordingly as the time comes around.

My problem is that the more outputs that I connect to lights in buildings, so the 12v power is reduced accordingly. Therefore if 12 output connections have 'on' times at the same time, the power to the 'on' outputs is reduced to 1 volt per output. In other words the power will fluctuate up and down as and when the clock switches each output on or off.

Any ideas how I can keep the power constant to each of the buildings?

Thanks in advance!

BTW Once this is resolved I have a similar problem with the other part of the system that controls night and day, sunrise sunset for the mains lights.
 

ci139

Joined Jul 11, 2016
799
there are many options
  • use ON terminals from clock to switch power from additional + or - 12V source
  • if the clock already switches the power from + or - 12V power rail you may be able to connect a higher power source to that rail and cut it off the remaining clock circuit ← requires knowing the insides of the clock or being able to find it's reference from www
 

ElectricSpidey

Joined Dec 2, 2017
739
Did the system always behave this way, or is it a malfunction?

Are you overloading the system power supply, this can be seen by measuring the systems main power supply under load.

A solution could be interfacing the outputs from the system with a second power source using load driver chips or relays.

Replacing the systems supply with a more powerful unit is also an option if the power supply is at fault.
 

Thread Starter

BJS171047

Joined Sep 18, 2019
6
Did the system always behave this way, or is it a malfunction?

Are you overloading the system power supply, this can be seen by measuring the systems main power supply under load.

A solution could be interfacing the outputs from the system with a second power source using load driver chips or relays.

Replacing the systems supply with a more powerful unit is also an option if the power supply is at fault.
Always behaved this way. I have been thinking that a second power source and relays could be the answer.
 

Thread Starter

BJS171047

Joined Sep 18, 2019
6
there are many options
  • use ON terminals from clock to switch power from additional + or - 12V source
  • if the clock already switches the power from + or - 12V power rail you may be able to connect a higher power source to that rail and cut it off the remaining clock circuit ← requires knowing the insides of the clock or being able to find it's reference from www
Hi. I think a higher external power source is the next thing to consider and I have been thinking that way. The clock switches power on and off but, as I say, that at its worst point could be as low as 1volt. Is that enough power to switch? I assume it will be?
 

crutschow

Joined Mar 14, 2008
23,523
The clock switches power on and off but, as I say, that at its worst point could be as low as 1volt. Is that enough power to switch?
I would assume if the clock is unloaded the output voltage will not vary significantly with the number that are on (?).

You can use the outputs to switch transistors at each output to control the lights powered by an external source.

What is the maximum current the lights will draw?
 

Thread Starter

BJS171047

Joined Sep 18, 2019
6
Hi
The lights will draw 12v, no more.
The schedule below shows the output connections and the times on and off and the fall off rate as it occurs. So the worst case is an output of 1.09v. I am thinking of attaching a non latching relay attached to each output with its own independent power source and using the (worst case) 1.09v to switch on and off the relay as power from the output turns on and off. That way the 12v power to each building is maintained constantly yet tripped on and off accordingly by the clock. (Sounds good in theory!)
Cheers....

Screenshot 2019-09-18 at 16.32.53.png
 

Thread Starter

BJS171047

Joined Sep 18, 2019
6
Hi
The bulbs require 12v. (Apologies, not sure what you need here.)
Yes, if the timer is not loaded with bulb loads its output voltage will remain constant and not drop.
Transistor or relay. I quite like relay as a solution but will look at transistors.
Thanks!
 

Bernard

Joined Aug 7, 2008
5,288
Do you have a multi meter & if so what is the highest current range ?
For a single transistor might connect it as an emitter follower, output will be about
1 V less than input. Or could use P ch. FET with an inverter ( IC with 6 stages ).
 

ci139

Joined Jul 11, 2016
799
Consult the shop for the model railway equipment if there is any nearby
((it may be they know your timer and what to do with it))
or the shop for relays (, transistors, etc.)

texting in the web is not that efficient

what you don't want to do is put the lighting control timer into heavy duty
-- e.g. don't test it with multiple outputs connected - such may damage it
 
Last edited:

crutschow

Joined Mar 14, 2008
23,523
The bulbs require 12v. (Apologies, not sure what you need here.)
That's the voltage (volts) they require.
I was interested in the current (amperes) they use when 12V is applied.
That can be measured with a multimeter set to measure current, placed in series (not in parallel:eek:) with the bulb.
I quite like relay as a solution but will look at transistors.
Relays are larger, more costly, and less reliable than transistors.
Their main advantage of relays is that they provide isolation between the control voltage and the output contacts, but that's not needed here.

Bernard's suggestion to use a BJT transistor as an emitter follower makes for a very simple circuit, and the 0.7V drop will likely not cause a significant reduction in the bulb light output.
Are the bulbs incandescent or LED?
 

eetech00

Joined Jun 8, 2013
1,726
I have a model railroad and wanting to simulate day and night, have lights in buildings turn on and off at the appropriate time, I purchased an electronic clock system from a company in the US. This was about 8 years ago and the company is no longer in existence.
The clock is a fast clock where the ratios can be altered so that 24 hours can be speeded up to be in an hour, 2 hours, 3 hours etc as required.
The system is 12v and has 14 outputs from which lights in buildings can be connected.
Each output has pre-determined on / off times, all of which are unique from each other. The purpose being that the building lights will go on and off at different times during the night times as triggered by the clock throughout a 24 hour cycle. In other words, individual building lights are triggered on and off accordingly as the time comes around.

My problem is that the more outputs that I connect to lights in buildings, so the 12v power is reduced accordingly. Therefore if 12 output connections have 'on' times at the same time, the power to the 'on' outputs is reduced to 1 volt per output. In other words the power will fluctuate up and down as and when the clock switches each output on or off.

Any ideas how I can keep the power constant to each of the buildings?

Thanks in advance!

BTW Once this is resolved I have a similar problem with the other part of the system that controls night and day, sunrise sunset for the mains lights.
Hi

You could use a p or n channel mosfet array chip(s). Each chip would provide 7 or 8 inputs to connect to your existing outputs and 7 or 8 high current outputs to drive the lights.it would draw very little current from the existing driver outputs.

Are the lights LED? Or?

eT
 
you can optimize the design with no base resistors (as hopefully) the emitter load provides base current . . . limiting -- but at switch ON such may blow with incandescent load
I understand the elimination of the resistor, but using that configuration has 2 potential problems.
One is as you say, and the other is any voltage droop at the timer output will be passed along to the bulbs.

It also pretty much eliminates using a load driver chip. (which eliminates having to place a resistor, if you choose the right driver chip)
 
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