Im at a loss about the 7555 output (see attached). When triggered, the Red LED stays partially on, along with the GREEN led, and the relay energizes. When not triggered the Green LED properly illuminates, and the Relay de-energizes.
So why is the red LED partially illuminating??
Thanks for the help.
Kim

 

So why is the red LED partially illuminating?

Probably because in normal use the output of a bipolar 555 is always at least a volt or so below the Vcc voltage.
You could try putting an ordinary diode in series with the red LED, or you could drive the red LED from the transistor collector instead of from Vcc.

Edit:
The 7555 is not bipolar, it's CMOS, So the first sentence above does not apply.

 

You have three problems.

1) Check to see how much current ICM7555 output can sink and source. This will determine if the 1 kΩ resistors are suitable.

2) When you drive LEDs from a logic output, do not use that output for something else. That is because the LED load prevents the output signal from reaching a proper logic LOW or HIGH level.

3) 10 kΩ resistor on the base of the transistor is too high. You need to assume a current gain of 10 to put the transistor into saturation mode. (See note 1). To turn the transistor off, you should also use a pulldown resistor at the base of the transistor.

 

Hi,
You could wire the red led and resistor across the relay coil.

 

The reason that the red LED illuminates is because current is passing thru it. That includes both the base current of the transistor and also the current thru the green LED. An LED is not simply a two state device. current flows whenever any voltage is present, and it does not take much current to produce a bit of light, at least with some LEDs.

 

Try connecting a 10k (or 1k) resistor across the Red LED (connect the resistor in parallel with the RED led) to divert some current so the LED turns off.

 

So why is the red LED partially illuminating??

A 7555 timer is a cmos device with a normal output practically the same as the supply voltage with no load.
The problem is the 7555 cannot source much current and depending on the load the voltage output will drop leaving a difference across the red LED and 1K resistor apparently enough to dimly illuminate.
Increasing the LED resistor values can eliminate the problem.

 

A 7555 timer is a cmos device with a normal output practically the same as the supply voltage with no load.
The problem is the 7555 cannot source much current and depending on the load the voltage output will drop leaving a difference across the red LED and 1K resistor apparently enough to dimly illuminate.
Increasing the LED resistor values can eliminate the problem.

Thank you, I shall try this

 

Firstly, remove the LED, 1k resistors and capacitor.
Get the relay working properly with a 1kΩ resistor instead of 10kΩ. Use LM555 or NE555 instead for higher current output.
We will worry about the LED later.

Edit: Sorry, I did not see the green LED. I mistook it for a capacitor.

 

Try this configuration if pin7 is available.

 

Try this configuration if pin7 is available.
View attachment 337555

I will shortly