ULN2803 Control

Akira

Hi friends.. I am new to this forum.. I am currently doing a project in my final year Manufacturing Processes and Automation Engg in Delhi (India). I have currently been able to acquire data from a submerged arc welding (ESAB Autoweld Major) machine using Advantech PCL818hg Daq card and Turbo c3. I would be grateful if you could give me some idea about relay controlling using ULN2803 as I am totally new to relay controlling. I need to controll the motors etc using this chip.
Awaiting replies

Post Edited By Moderator (Jon Williams (Parallax)) : 10/1/2005 12:53:13 PM GMT

Jon Williams

The ULN2x03 is very easy to control: put a high signal (+5) on an input and the output will connect (through a Darlington) to ground allowin a device connected between in and the positive side of your device supply to operate.

This article will help: http://www.parallax.com/dl/docs/cols/nv/vol1/col/nv6.pdf

▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
Jon Williams
Applications Engineer, Parallax

LoopyByteloose

Akira,
If you want to control more than 500ma total with the ULN2803, it is not possible. If you have 8 relays at 20-25ma each, it is no problem. If you have two stepper motors that only have 50% of the IC turned on, you can go to 40-50ma each.

It gets too hot when the current goes much higher. In that case, you may have to use individual Darlington Transistors or MOSfets. Both are easily available and the MOSfets run a bit cooler [noparse][[/noparse]which is useful in a hot climate and a welding environment].

The MOSfets can be a bit more demanding of engineering as they have high internal capacitances and the combined internal capacitances and internal resistances limit them to something like 10Mhz and below.

▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
"When all think alike, no one is thinking very much.' - Walter Lippmann (1889-1974)

······································································ Warm regards,····· G. Herzog [noparse][[/noparse]·黃鶴 ]·in Taiwan