Darlington Arrays

[Michael]

Hi,

Am I right in thinking that the ULN2003A has built in base resistors meaning
I can drive a bank (6) of relays with the only external components being one
diode per relay? I assume a 1N4001 is good enough?

Cheers,

Michael

 

[ian field]

Hi,

Am I right in thinking that the ULN2003A has built in base resistors
meaning I can drive a bank (6) of relays with the only external components
being one diode per relay? I assume a 1N4001 is good enough?

Cheers,

Michael

First hit on google..............

http://focus.ti.com/lit/ds/symlink/uln2003a.pdf

 

[John Larkin]

Hi,

Am I right in thinking that the ULN2003A has built in base resistors meaning
I can drive a bank (6) of relays with the only external components being one
diode per relay? I assume a 1N4001 is good enough?

Cheers,

Michael

The ULN even has the diodes.

John

 

[Michael]

First hit on google..............

http://focus.ti.com/lit/ds/symlink/uln2003a.pdf

Thanks, but what's the thing that looks like a NOT gate symbol? The the
symbol for a darlington pair?

 

[ian field]

Thanks, but what's the thing that looks like a NOT gate symbol? The the
symbol for a darlington pair?

Read further down the data sheet - it shows the internal diagrams for each
darlington stage for 01,02 & 03 versions.

 

[Peter Bennett]

Thanks, but what's the thing that looks like a NOT gate symbol? The the
symbol for a darlington pair?

From a logic designer's viewpoint, these parts are groups of
inverters, as shown in the logic diagram on page 2 of that data sheet.
Page 3 shows the actual circuit of one inverter, for each of the
varieties of the part.

The 2003 input circuit makes it TTL-compatible. The 2002 and 2004 are
designed to be driven from other sources. An old Motorola datasheet
(perhaps Freescale now) listed the intended driving sources for each
variety.

By the way, there's an 8-channel version: ULN2803.

These parts include diodes, so you don't need an external one.

--
Peter Bennett, VE7CEI
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[Chris]

The ULN even has the diodes.

John

Yup. There's a diode for every output on the ULN2003. Remember -- to
take advantage, though, you have to connect pin 16 to Vcc (or the
power source for the relay coils).

Good luck
Chris

 

[Jamie]

Hi,

Am I right in thinking that the ULN2003A has built in base resistors meaning
I can drive a bank (6) of relays with the only external components being one
diode per relay? I assume a 1N4001 is good enough?

Cheers,

Michael

All the outputs are open collector and pull to the (E) pin when on.
the (E) pin needs to be connected to your supply's common/(-)

They all have an internal diode for each already, also, it has
a diode array tied to a "COM" common pin. With that control, you can
connect the "COM" to the (-) rail and all of
the outputs will turn on or, connect "COM" to the (+) rail and they'll
aid in protection.

One leg of each relay are joined all together to the (+) of your
supply. Each remaining leg of the relays will connect to a single
output.

Hope that was clear enough.

 

[ehsjr]

Yup. There's a diode for every output on the ULN2003. Remember -- to
take advantage, though, you have to connect pin 16 to Vcc (or the
power source for the relay coils).

Good luck
Chris

Pin 9, not 16.

 

[Chris]

Pin 9, not 16.- Hide quoted text -

- Show quoted text -

Oops, right. Thanks -- hope the OP took a look at the .pdf above and
got it right.

Cheers
Chris