about uln 2003/ uln 2803 drivers and relays

sir, Im swetha doing m.tech.My project is hand gesture recognition. In this i wll give 4 gestures as input to the dsp and according to it one of the led's of dsp tmsc6713 processor will glow. upto this i have done. Now i need to connect one truck to the dsp processor and make it move in different directions according to the input gestures. one of my sir's suggested me to use a relay and an IC.. I have checked the voltage and current of dsk c6713 processor and it was 3.3v and 0.33ma.. but to make the truck move i need 3.6v and 5.6ma current...so can you suggest me which relay and IC can i use to drive the road roller/ truck so that the processor wont get damaged.... sir, can i use uln 2003/ uln 2004/ uln 2803 IC? what type of relay i must use? can you provide me any circuit diagram connection of ic and relay?
Thank You.

5mA load can be driven without a relay, just by a single transitor (2n2222) ..
Put 10k resistor between the base and use external 3.6V supply ..
See picture below ..
More at:
Using Transistor as a Switch | ermicroblog

IanP
:wink:

thank you for your reply sir...But, instead of using transistors can i use any relay ,because our project guide is very particular about using the relay and the IC ...So can you suggest me which relay and ic can i use for my project..actually i need 4 relays for truck to move..so can i go with uln2003 or i must use uln2803? actually i didnt find the difference between two and can you please say the name of the relay i should use?
thank you.

I think they are the same, ULN2803 was the older version, you can use the following connection diagram, you can connect any relay to the outputs, ULN2003 output should be connected to the gnd of the relay control.



Alex

swetha reddy said:

thank you for your reply sir...But, instead of using transistors can i use any relay ,because our project guide is very particular about using the relay and the IC ...So can you suggest me which relay and ic can i use for my project..actually i need 4 relays for truck to move..so can i go with uln2003 or i must use uln2803? actually i didnt find the difference between two and can you please say the name of the relay i should use? thank you.

Click to expand...

Why to use Relay when they are not required? Buy some relays, use the simplest method to work the circuit as "IanP" and "Alexan" sugested ,and Donate those relays to the guide. Striclty ask him to answer why to use a long way while you have a easier way out.? Actually project guides in India make students to make / bring new concepts and projects and get themselves involved and get new ideas. Actaully your guide wants to study how to use a relay. Help him. Cheers

ok thank you sir.. Ill go with it.

---------- Post added at 06:49 ---------- Previous post was at 06:38 ----------

Actually i asked my guide why to use relays . he replied me that by using relays, the dsp kit wont get damaged and also he said something like if we use relays power supply comes directly from battery.... like that...which actually i didn't get his point.. anyhow ok sir ill go with the above circuit...

pranam77 said:

Why to use Relay when they are not required? Buy some relays, use the simplest method to work the circuit as "IanP" and "Alexan" sugested ,and Donate those relays to the guide. Striclty ask him to answer why to use a long way while you have a easier way out.? Actually project guides in India make students to make / bring new concepts and projects and get themselves involved and get new ideas. Actaully your guide wants to study how to use a relay. Help him. Cheers

Click to expand...

hi Pranam77 Sir...! (I think you are not in south india)
Yesterday, A student batch aproch me for project. thier Guide also telling the same one... Actually sir, In a students point of view, They are newable to troubleshoot if any problem comes. (Some Guides also dont have practical exp.) If they use relay means that mechannical contact of "CLICK" sound prepare them mentally good. If some other means, if not working They mudt trace the circuit & check all voltage levels... that may not know sudent (even guide). So simply they didnt accept...