Need help with using a transistor or triac as a switch

[MAJ]

Hello everyone,

I have a digital programmable timer with signal output of 1.2V DC. It runs on rechargeable battery of 1.2V. I need to use this small output to run a small 6V relay. To my general knowledge, I need at least 3 volts to trigger a small transistor. Is there a transistor that can be triggered by 1.2V signal? or can I use a photoisolator triac to drive the relay with the small 1.2V signal? Thanks.

 

[audioguru2]

Same question again but on this forum.

Here you forgot to say which relay you will use so we do not know its coil current then we cannot calculate how much input current a transistor needs.

You also did not say how much current the 1.2V timer can produce which might not be enough current to drive the transistor.

1.2V is probably too low to activate a photo-triac.

 

[MAJ]

Hello Audioguru, and thanks for your reply. Attached is the data sheet of the relay I have. The model is SRD-06VDC-SL-C. I do not know how much current the timer can provide. I hope there is a way/component that can be triggered by the 1.2V output. Otherwise, I will have to buy a new timer, but I am really interested to get the timer I have to work, of course if possible.

 

[HarryA1]

Lets see if this is readable. Using a 2n2222 - about 10 cents apiece. Current from the source is 40ma with a base resistor of 1000 or 10k.

In the view the yellow trace is the current through the relay; scale on the right . Green is the voltage at the base; scale on the left. I  have no idea what the inductance would be so I set it at 0.001 henry.

 

[audioguru2]

Your simulation is cheating because it uses a very high base voltage that has almost unlimited current and no voltage drop.

 

[MAJ]

Hello everyone,

I got a suggested simple NPN circuit that worked fine with the 1.2V trigger signal. Here it is



Thanks everyone.