Need help with using a transistor or triac as a switch

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M

MAJ

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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.
 
What is the current required by the relay for activation? Or, manufacturer and part number? Can you post a datasheet?

ak
 
AnalogKid said:
What is the current required by the relay for activation? Or, manufacturer and part number? Can you post a datasheet?

ak
Click to expand...
Hello AK, Attached is the datasheet. The model is SRD-06VDC-SL-C.
 

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The input of a transistor needs at least 0.7V with a current of at least 6mA for it to turn on your 60mA relay coil.
Can your timer produce this voltage and current? Please post the datasheet of your timer.
 
1.2V is plenty to turn on almost any bipolar transistor to act as a switch but, from the relay datasheet, a minimum of 4.5V is needed to operate the 6V relay. Do you have a 4.5V (or higher) supply as well as the 1.2V cell?
 
Yes, I have a 6V DC supply board that I can fit inside the timer box, so that it powers the relay, and (after stepping down the voltage) charge the rechargeable 1.2V battery.
 
Providing your timer can source about 6mA a circuit like this should be able to operate the relay.
 
If the timer can't source 6mA, you can add a PNP transistor gain stage (below) to reduce the required input current to about 0.6mA.

 
What is the timer that can have a load and an output at its supply rail of 1.2V when the battery powering it is only 1.2V?
Most electronic circuits have a voltage drop when driving a load.

An old Ni-Cad cell or modern Ni-MH cell is 1.2V when half discharged. Then the transistor might not work when the battery drops to 1V.
 
audioguru said:
What is the timer that can have a load and an output at its supply rail of 1.2V when the battery powering it is only 1.2V?
Most electronic circuits have a voltage drop when driving a load.
Click to expand...

Presumably it's an FET switch, so no voltage drop as such.
 
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