Continue to Site

Welcome to our site!

Electro Tech is an online community (with over 170,000 members) who enjoy talking about and building electronic circuits, projects and gadgets. To participate you need to register. Registration is free. Click here to register now.

  • Welcome to our site! Electro Tech is an online community (with over 170,000 members) who enjoy talking about and building electronic circuits, projects and gadgets. To participate you need to register. Registration is free. Click here to register now.

Uln2003

Status
Not open for further replies.

joshua17ss2

New Member
hey
im working on a project that will control 20 SSRs operating at 24 volts.
the relay board has a single input for the 24volt relay control circuit, and only require a short between the ground and the control pin for the selected relay. 24 volts will flow thought this short. i want to allow a microcontroller to run these relays i originally planned to use simple switching transistors to control each of the lines, but i wanted to use an IC as it would provide and neater circuit and less components.

Could i use the ULN2003 to contor the lines by just connecting the control pin for the the relay to the control pin on the uln chip.

Any help or ideas would be appriciated, i attached a image detailing the way i think it would be wired..
thanks
josh
 

Attachments

  • image003.JPG
    image003.JPG
    36.2 KB · Views: 5,523
It should work ok, If the relays don't have a transcient protection diode across the coils I would connect the common pin of the ULN2003 to +24 so the internal diodes are the protection diodes.
 
that is exactly what the uln2003 is for. just tie off the common pin to the 24V supply and you are off to the races.
 
well the problem i saw was that the ssr board uses a common ground and has its own power hook up,
so can the uln provide me with the short needed to trigger the solid state relays on this board

thanks
josh
 
Since your relays are solid state (no inductor), then you don't need to connect the common pin to +24. Your design will work fine.
 
I bought the board and relays on ebay, i was looking to get some logic level relays but there 5 to 10 dollars a piece, i only paid 10 dollars for 20 relays and the board, i figure the buffer i need to make is well worth the savings. :)
I already have a pile of the uln chips i use them in alot of my projects they are a great little chip.
 
What are you controlling with the relays?

I will be using the relays to control a bunch of lights. i do small shows for christmas, halloween and any other time i find a theme.
This way i can move all the lighting control to a pic all its own. and connect them to the computer or another pic thats running the air valves, motors and everything else in the show.
 
**broken link removed**

this is the board i was using to control just 8 channels of lights before, im hoping that the ssr board will be much neater, and more compact and faster :) along with tripeling my availible channels.
i will post come pictures of the new board when it is finshed, (that will be in a few months as all my electronics are packed and waiting to be moved to orlando.)
 
Last edited:
I made a Christmas light controller with a 555, 4017 and 4N25 optos in 1988. Only had to replace the interface board after a small fire in 1997. That project is boxed away after 3 years of no lights hung up. A schematic is available, and can be interfaced with ULN2003A for other applications.
 
im hoping my design will have significanly less parts, the controller, the buffers, and the relay board
Small parts count, easy wiring. and im using at 18F4550 so if i need to i can control it from my computer, at the moment im happy just writing the code for the microcontroller.
since i will have the extra ports im thinking of adding an lcd and RF remote to select different shows on the controller.
 
Hello gramo,

What program you are using to draw electrical circuit it seems interesting
 
Hello there,

Hope you will be doing fine.I am in need of some help regarding ULN2003 operation with MSC1200 Microcontroller. I am using ULN2003 to control Relay (PE014F05-PCB, SPCO, 5VDC). Could you please advise me about the ULN2003A input circuit, can i directly connect the MSC 1200 port pins to input pins of ULN2003A? Or I have to do some thing else to drive relay from MSC1200 using ULN2003. ULN2003 will be power by 5VD. please do help me out, i will be very thankful to you.

Kind regards
Asif
 
asif418 said:
Could you please advise me about the ULN2003A input circuit

Do you mean something like this?
**broken link removed**

The ULN2003 can be driven by logic voltages to provide an earth to the target circuit when a logic High is present at the input.

You must connect Pin 9 of the ULN2003 to the positive supply of the relay to shunt back emf
 
Why don't you look at the datasheet for the ULN2003A?
It tells you all about it.

Of course it can be driven directly from an output of a micro-controller like a PIC.
See if your micro-controller has an output current of at least 125uA.

But a ULN2003 has a voltage loss of about 0.8V at the low current for a relay so the 5V relay might not work.
 
Hello There,

Yes I have checked the data sheet, but i am not confident that if i connect the MSC1200 port pins directly to the ULN2003A base (input) pins then the MSC port pins will be able to drive the ULN2003A. I have attached part of circuit diagram with this reply, hope this will give you clear picture and you will be in better position to help me out. The only thing I am intrested to know is that is this circuit OK? and if i directly connect the MCU pins to ULN2003A pins will MCU pins be able to drive the ULN2003A? or i have to pull up the p0 and p1 in order to drive the ULN2003A.

Many thanks in advance, looking forward to your suggestions and help.

Best regards
Asif
 

Attachments

  • ULN2003A circuit.GIF
    ULN2003A circuit.GIF
    9 KB · Views: 8,601
ULN2003 circuit

Hello There,

Yes I have checked the data sheet, but i am not confident that if i connect the MSC1200 port pins directly to the ULN2003A base (input) pins then the MSC port pins will be able to drive the ULN2003A. I have attached part of circuit diagram with this reply, hope this will give you clear picture and you will be in better position to help me out. The only thing I am intrested to know is that is this circuit OK? and if i directly connect the MCU pins to ULN2003A pins will MCU pins be able to drive the ULN2003A? or i have to pull up the p0 and p1 in order to drive the ULN2003A.

Many thanks in advance, looking forward to your suggestions and help.

Best regards
Asif
 

Attachments

  • ULN2003A circuit.GIF
    ULN2003A circuit.GIF
    9 KB · Views: 1,069
Hello There,

Yes I have checked the data sheet, but i am not confident that if i connect the MSC1200 port pins directly to the ULN2003A base (input) pins then the MSC port pins will be able to drive the ULN2003A. I have attached part of circuit diagram with this reply, hope this will give you clear picture and you will be in better position to help me out. The only thing I am intrested to know is that is this circuit OK? and if i directly connect the MCU pins to ULN2003A pins will MCU pins be able to drive the ULN2003A? or i have to pull up the p0 and p1 in order to drive the ULN2003A.

Many thanks in advance, looking forward to your suggestions and help.

Best regards
Asif

hi,
look at these images.

Why have you connected the ULN drivers in parallel.?

What is the current or resistance of the relay coil.?
 

Attachments

  • esp04 Jan. 13.gif
    esp04 Jan. 13.gif
    30.4 KB · Views: 1,227
  • esp03 Jan. 13.gif
    esp03 Jan. 13.gif
    6.8 KB · Views: 631
  • esp05 Jan. 13.gif
    esp05 Jan. 13.gif
    20.6 KB · Views: 673
Last edited:
Hello,
I am using TYCO ELECTRONICS PE014F05 5V SPCO PCB relay. https://www.electro-tech-online.com/custompdfs/2009/01/63899.pdf
Coil resistance is 125 OHM (datasheet) and verified by multimeter. coil power is 200mW. why i connect ULN drivers in parallel is to increase the current to the coil. The relay is a Single Pole Change Over relay ie if coil power is removed it maintain its last state and in my circuit i just have to power the relay for 30ms to 40ms. But if you have any better idea plz do tell me. Other main factor i am afraid of is that if i directly connect MSC1200 port pins to ULN will that work or i have to pull up the MCU pins in order to make circuit working. Any suggestion/ideas/help??????

Best regards

Asif
 
Status
Not open for further replies.

Latest threads

New Articles From Microcontroller Tips

Back
Top