Li_ereunpisan
Full Member level 5
- Joined
- Jul 14, 2009
- Messages
- 260
- Helped
- 32
- Reputation
- 64
- Reaction score
- 28
- Trophy points
- 1,308
- Location
- Bandung, Indonesia
- Activity points
- 2,768
Follow along with the video below to see how to install our site as a web app on your home screen.
Note: This feature may not be available in some browsers.
No, won't work. You need 12mA high drive (from +5V to the 12 inputs).what if the picture?
You could use Q1 as emitter-follower: Collector to +5V, emitter to the 12 inputs. And so you don't need to take care of the logic inversion by the transistor (an emitter-follower doesn't invert the logic state, your above circuit does).or you have other recommendations?
if you mean like thisNo, won't work. You need 12mA high drive (from +5V to the 12 inputs).
You could use Q1 as emitter-follower: Collector to +5V, emitter to the 12 inputs. And so you don't need to take care of the logic inversion by the transistor (an emitter-follower doesn't invert the logic state, your above circuit does).
Don't connect input pins#1 if you don't use their outputs.
Each relay shouldn't need more than 80mA (max. current of one ULN2003 ≦ 500mA).
Why do you want to turn on so many relays simultaneously? Why use so many switches when a single MOSFET would do the job?
Keith
I use a diode for reverse current protection, and the switch voltage is 48VdcYour diodes are also backwards. How much current and voltage do you need to switch?
Your second version with NPN driver needs a pull-up resistor, diodes need to be reversed and then it will work .. see attached picture ..
As an alternative consider single MOSFET or NPN that can drive all relays connected in parallel (see Keith's thread) ..
:wink:
IanP
The diodes are of course needed . Even the pull up resistors , why dont you try out the npn transistor solution ?
Yes, I think this should work.
Not necessarily: The ULN2003 has built-in diodes for each channel, strong enough for the permitted currents.The diodes are of course needed.
Not necessarily: The ULN2003 has built-in diodes for each channel, strong enough for the permitted currents.