3 volt instant on - 3-5 minutes delay off for simple model train (non energized tracks)

Thread Starter

advarp

Joined Jan 12, 2018
57
Hi there,

1) I have a cheap Xmas train set runnign on non-energised plastic tracks. The engine takes two AA batteries and has a switch forward / reverse / stop on it. The two batteries drive a 3 Volt electric motore who drives the wheels via a worm mechanism.That is all :)

Now, I woudl like to be able to push a switch (original or other) and the train to run for say 3 to 5 minutes after which to stop until the switch is pressed again or cycled.

The problem is that I have 3 volts available only and there shoyudl be very small current drawn after the delay time has elapsed and thew circuit switches off, so no relays.. although I have a small electric motor in there (it is a small train set with 3 carriages only so low amp draw when on)

It can be done with a 555 probably, but no idea how... I can solder and test with multimeter etc but circuit design...

2) Actually - I realised I actually need something similar for my car in case someone leaves the door or boot open - the circuit should turn on instantly and then switch off ater 10 minutes (longer time) even if the trigger is still on (door still open) - new cars have this feature to avoid battery drain. Again the current drain should be quite l;os once tghe circuit has switched off - so having a NC relay and using a typical delay on circuit woudl have the relay coil energised indefinitely which, with LED interior lights, will draw more current than the lights them selves :)

So, similar circuits except the delay time and operating voltage (3V vs 12v)...

-------
For 2) Yes, I have seen this


Will it do for the car application, although the reed relay will drain extra current? The new LED interior lights draw very small current... so no relay necessary and low current drain when activated would be required (else no sense in doing the whole thing). Is there really no simpler circuit I can use I wonder...
 

AlbertHall

Joined Jun 4, 2014
10,586
The circuit below will do the job with some modifications. You could remove the relay and replace it with your train motor. You should use a TIP120 for the Q2 position which will handle higher currents and values will need to be changed to get the desired time delay.
 

crutschow

Joined Mar 14, 2008
25,700
The circuit below will do the job with some modifications.
I don't see now that can be adjusted to give a 3-5 minute delay. :confused:

This is my preferred circuit (Version 2) for delay times over a minute.
It uses relatively small capacitors and is easy to set the time delay.
The relay is off after the time out, so draws essentially no current after that.
 

AlbertHall

Joined Jun 4, 2014
10,586
I don't see now that can be adjusted to give a 3-5 minute delay. :confused:

This is my preferred circuit (Version 2) for delay times over a minute.
It uses relatively small capacitors and is easy to set the time delay.
The relay is off after the time out, so draws essentially no current after that.
The 4060 minimum supply voltage is 3V and the requirement is that it should run from a 3V battery so there is not much margin for the battery running down.
 

crutschow

Joined Mar 14, 2008
25,700
The 4060 minimum supply voltage is 3V and the requirement is that it should run from a 3V battery so there is not much margin for the battery running down.
The Vgs threshold voltage for the CD4000 series varies from 0.7V min. to 2.8V max.
Typically then, it should work below 3V (to about 1.5V), but worst-case would be about 2.8V.
So what are the chances of having a worst-case chip?
 

AlbertHall

Joined Jun 4, 2014
10,586
The ideal chip for this would be the CSS555C - very long times available and operation down to 1.2V and very low supply current.
The only problem is that you need the kit to program it :(
 

AnalogKid

Joined Aug 1, 2013
8,708
1) I have a cheap Xmas train set runnign on non-energised plastic tracks. The engine takes two AA batteries and has a switch forward / reverse / stop on it. The two batteries drive a 3 Volt electric motor who drives the wheels via a worm mechanism.
Any idea what the motor current is?

ak
 

Thread Starter

advarp

Joined Jan 12, 2018
57
Thanks for all the responses!

I know, it's not easy due to the 3Volt issue... I've been looking at this for several years now, always before Xmas of course lol. Voltage woudl drop when the engine runs of course... I use AA rechargeables but rarely switch the train on as someone has to be around to stop it etc. It even plays Xmas songs (badly lol).

Re motor - well - I could try to measure the current, I only have a small multimeter and I might blow its fuse (small volts -> sizeable current, right?). Anyway I'll go dig out the train set from the Xmas pile and try to measure :)

Some train kits come with a timer and even remote but probably run at higher voltage, bigger batteries etc. This is a just a cheap kit from Aldi. In the past i had a whole small city with proper 12mm gauge trains (made in Eastern Germany :)) but gone are those days unfortunately - maybe at retirement...
\
EDIT: https://www.ebay.com.au/itm/NEW-Chr...505000?hash=item3d527688a8:g:qbMAAOSwxixaMyN3

Get this one and rip out the remote (as this one is not really an Xmas train)? :) Alternative to timer - haha
 

crutschow

Joined Mar 14, 2008
25,700
Then how about an LMC555 CMOS timer, which can work down to 1.5V?
You should be able to get near 5 minutes with a 1 megohm charge resistor and a 270μF cap.
 

crutschow

Joined Mar 14, 2008
25,700
Given the high leakage currents of electrolytic/tantalum caps it might be better to use a 10Mohm (or higher) timing resistor with one or more large (e.g. 10μF) ceramic or film capacitors if using the LMC555.
 

Thread Starter

advarp

Joined Jan 12, 2018
57
Any chance of a simple schematic ?? With some power transistor / small relay to control the electric motor of course :)

By the way on Ebay I can see all simple trains are 3V , while the remote control ones seem to be 6V (4xAA), so maybe it is the wrong question to ask for 3V powered trains :) I am sure there would be some miniature COB solution like e.g. the 6/24 timers on electric candles or Xmas lights, but I did not see any such low volt kits anywhere
 

crutschow

Joined Mar 14, 2008
25,700
Any chance of a simple schematic ??
Below is the LTspice simulation for a delay using an LMC555 equivalent.
It uses a transistor at the output to drive a typical 3V, 60Ω relay.
The ON time is about 240s after power is applied for the R2C1 values shown.

upload_2018-1-12_20-58-9.png
 

be80be

Joined Jul 5, 2008
2,049
You don't even need a relay I bet the motor stall current is nothing maybe 400mA run probably 100mA or less
I'd use a 10F200 and be done with it.
2 resistors one diode a 2n2222 and 1 cap
Run the 10F200 off the 3 volt supply set to sleep till button pressed
 

crutschow

Joined Mar 14, 2008
25,700
Below is a variation on the circuit that solves the slow reset problem noted by AK.
It uses the DIS terminal to instantly reset C1 at the end of the timeout.

upload_2018-1-12_23-44-11.png
 
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