Common pwm pins on 18 project board

[Markbishop16]

Picaxe 18m2+, Picaxe 18 project board, not high power

I have a simple project that at maximum current may draw 600 ma which is 100 ma more than the project board output.

Max load will operate for seven seconds then it will reduce using pwm, the lower constant current will be nearer 380 ma this will be on for 3 hours before turning off.

Can I common B.3 and B.6 to share the load.

Thanks.

 

[Goeytex]

The Datasheet is your best friend.

From the ULN2803 Datasheet:

The ULN2803A device is a high-voltage, high-current
Darlington transistor array. The device consists of
eight npn Darlington pairs that feature high-voltage
outputs with common-cathode clamp diodes for
switching inductive loads. The collector-current rating
each Darlington pair is 500 mA. Logic pairs may be
connected in parallel for higher current capability.

Another thing you can do to reduce thermal stress on the ULN2803 is to glue a
heat sink on top of the chip with thermal epoxy. I use "Arctic Silver" brand
but there are others that will work as well.

 

[Markbishop16]

Thank you for the reply it was the pwm operation I was worried about.

I have wired them together and will leave it running, to see how warm it gets.

 

[Technical]

We would connect one PICAXE output to two ULN2803A inputs (e.g.by bending a leg out of the ULN2803A socket and soldering it across).
We would not recommend simply joining two PICAXE PWM outputs together, they may not be quite in sync.

 

[Markbishop16]

Thanks for the great idea.
I will change the boards and use this way for safety.

 

[Dartmoor]

I can back up the suggestion from Technical Support (one PICAXE output to two ULN2803A inputs).
I have done this with a motor controller and it works well.