Hi All

Sorry in advance if the questions below have been answered elsewhere

I bought some logic delay circuit boards on ebay whic said they could be used to control the power to a model railway and thus I could use them to stop the train at the station by use of read switches. and then after a selected time period start the train again having changed the signals automatically in the mean time.

However when I came to set it all up there seemed to be no power to the line at all from the module. When checked with the trusty multi-meter it turns out that the module does not provide enough current to drive the model train (approx 500mA needed)

I know that I need to put a relay between the module output and the power to the line but don't have a clue what relay I need other than a SPST normally closed relay

The input (switching i presume) details are 2 to 3v @ approx 1mA which will then allow power to the line of 5 to 12v @ max of 500mA

BTW live in the uk so if anybody can tell me what i need to buy of ebay or Maplins I would be most grateful

Thanx in Advance

Steve

 

Do you have an ebay link?
You may just need to add a power transistor?
Max.

 

The ebay link for the logic module is

http://stores.ebay.com.hk/WEHONEST/InstructionOfAutoDelaySwitchBoard.html

but It annoyingly doesn't provide the operating output currents hence having to get the multi meter out to find out why the train did not move during the normal on state (A)

Thanks for looking at this

Steve

 

Must admit I have not a clue about the use of transistors

 

Just taken Transisitors 101. I think if I use a 2N3906 PNP general purpose amplifier transisitor with a 5v supply, R1 of 1K Ohm connected to the collector and R2 of 10K Ohms between the collector and supply. I should be a happy bunny with a more stable and enduring solution. Thanks for the Tip

 

The 2N3906 is only rated for 200mA collector current (maximum) - but a more realistic maximum design current is half of that, or 100mA - when the base is supplied 1/10th of the desired collector current. You say you just have a few mA available, so that's not going to cut it.

Here's a datasheet for the 2N3906:
http://www.fairchildsemi.com/ds/2N/2N3906.pdf
Have a look at Page 4, Figure 2. Collector-Emitter Saturation Voltage vs.
Collector Current.

You haven't made it clear just how MUCH current is available, and at what VOLTAGE when that much current is flowing out of the "relay".

In the Ebay listing, it appears that the time-delay "relay" was meant to just control LED lighting, as in aspect signals, crossing signals and the like. LEDs might generate sufficient light with just a couple of mA current flowing through them. You obviously need far more than that.