Hi there
I am helping a friend out who is going to be doing a bit of charity work.
For this he needs a prop. I am doing the minor bit of electronics that
will add a bit of 'bling' to it. I have a 555/4026 circuit driving 8 Red LED's
at the moment on my breadboard. Now the thing is it will actually need
Blue LED's to be accurate and there lies the rub. I know that different
colour LED's have slight differences in current draw etc etc.
The circuit is running without resistors in series with the LED's as per the
diagram I used off the net. But if I use Blue LED's would I need resistors
in line or will I actually need to use a transistor at each output to handle
the LED's in the event that the 4026 can't deal with the demands of the
blue's.
I have found some blue LED's that are not as bright as the sun. Here are the specs could you please advise me as to whether the 4026 could handle them or will I need to insert transistors.
Specifications:
Order Code JA24B: Diffused Blue
Kingbright description: L-53MBD
Viewing angle: 60°
Forward voltage at If=20mA: 4.0V
Forward current max.: 30mA
Reverse voltage max.: 5V
Wavelength @ peak : 430nm
Power dissipation PT: 105mW
Light output min.@ 20mA: 40mcd
Light output typ.@ 20mA: 60mcd
The red LED's I am using are from a cheap diy kit so I have no idea what their ratings are to compare.
I have seen a 4017 chaser circuit that uses transistors at the outputs so know how to set that up if required with the 4026. I think BC547 would do.
regards
Fenris
I am helping a friend out who is going to be doing a bit of charity work.
For this he needs a prop. I am doing the minor bit of electronics that
will add a bit of 'bling' to it. I have a 555/4026 circuit driving 8 Red LED's
at the moment on my breadboard. Now the thing is it will actually need
Blue LED's to be accurate and there lies the rub. I know that different
colour LED's have slight differences in current draw etc etc.
The circuit is running without resistors in series with the LED's as per the
diagram I used off the net. But if I use Blue LED's would I need resistors
in line or will I actually need to use a transistor at each output to handle
the LED's in the event that the 4026 can't deal with the demands of the
blue's.
I have found some blue LED's that are not as bright as the sun. Here are the specs could you please advise me as to whether the 4026 could handle them or will I need to insert transistors.
Specifications:
Order Code JA24B: Diffused Blue
Kingbright description: L-53MBD
Viewing angle: 60°
Forward voltage at If=20mA: 4.0V
Forward current max.: 30mA
Reverse voltage max.: 5V
Wavelength @ peak : 430nm
Power dissipation PT: 105mW
Light output min.@ 20mA: 40mcd
Light output typ.@ 20mA: 60mcd
The red LED's I am using are from a cheap diy kit so I have no idea what their ratings are to compare.
I have seen a 4017 chaser circuit that uses transistors at the outputs so know how to set that up if required with the 4026. I think BC547 would do.
regards
Fenris