Maker Pro
Maker Pro

CD4017 Driving a Relay

P

prizark

Jan 1, 1970
0
Hi guys,

I am using the CD4017 Johnson decade counter in on of my
experiments.I want to turn the relay on during the 4th to 6th clock
pulses of the counting.So I used an OR gate to input the "output 4",
"output 5" and "output 6" of the 4017 to drive the realy from there.
The OR gate is made by using DL(Diode Logic) just a couple of zener
diodes and a pulldown resistor. I know that the output driving current
of the CD4017 is not more than 9mA but it is sufficient to drive and
transistor into saturation and switch on the relay. But for some
reason that is not happening. The circuit is able to drive LED's with
and without transistor at the output but not the relay.The relay is a
6V/100 Ohms type.I even tried using a Darlington pair and also the
intergrated version of the Darlington pair(ULN2803) but couldn't make
things any better. What could be the problem.

Thankx,
prizark.
 
K

Kevin Weddle

Jan 1, 1970
0
A zener diode doesn't guarantee 5 volts. It will produce 5 volts when
the voltage exceeds 5 volts.
 
K

Kevin Weddle

Jan 1, 1970
0
Also, if the logic is alright, the diodes still require a minimum current.
 
F

Frank Pickens

Jan 1, 1970
0
prizark said:
Hi guys,

I am using the CD4017 Johnson decade counter in on of my
experiments.I want to turn the relay on during the 4th to 6th clock
pulses of the counting.So I used an OR gate to input the "output 4",
"output 5" and "output 6" of the 4017 to drive the realy from there.
The OR gate is made by using DL(Diode Logic) just a couple of zener
diodes and a pulldown resistor. I know that the output driving current
of the CD4017 is not more than 9mA but it is sufficient to drive and
transistor into saturation and switch on the relay. But for some
reason that is not happening. The circuit is able to drive LED's with
and without transistor at the output but not the relay.The relay is a
6V/100 Ohms type.I even tried using a Darlington pair and also the
intergrated version of the Darlington pair(ULN2803) but couldn't make
things any better. What could be the problem.

Thankx,
prizark.

Try replacing the zener diodes with a couple of small signal diodes such
as 1N4148 or 1N914. If I understand what you are saying I fail to see
why you are using zeners.
fp
 
Top