Relay acting screwy - Page 2 - Electronic Circuits Projects Diagrams Free

2camjohn · 5th August 2004, 04:09 PM

Quote:

Originally Posted by Johnson777717

Quote:

So my transistor was protected and Johnson is trying his best to hijack my thread.

Relax, just asking a question.

A little knowledge is a dangerous thing. I'm living proof :twisted: :twisted:

TillEulenspiegel · 5th August 2004, 05:22 PM

Quote:

Originally Posted by 2camjohn

Thanks for all the help guys, I will do the tests now.

I thought the test I have already performed was sufficient to rule out the transistor: Using an almost dead pp3 to power the motor stopped the relay holding ON at all.

The relay is definately a 6V, but the click is nowhere near as audible as other identical relays I have on other boards.

I like the idea of using optocouplers, but they seem to be such tiny devices.
Can they handle alot of power?

Does anyone have any links to websites which cover optocouplers.
Eventually I want to be able to switch 2A at 9V with a 6V signal.

Ill post back once I have done the tests.
Cheers
John

Opto relays: http://www.mpja.com/listitems.asp?dept=133&main=132

2camjohn · 5th August 2004, 07:15 PM

Cheers dude,

But I have a small optocoupler here http://www.optocomponents.com/Quicklist4/SFH618A-2.htm

Could i use this with a couple of transistors to produce the results I want (Switching 2A @ 9V with a signal of 6V)

Thanks

TillEulenspiegel · 5th August 2004, 10:42 PM

Yes if you want , I'd use a TIP120, It's a darlington pair in a to-220 case ( sorry American convention) , but there are solid state relays that will do the job and all they need is a 3-30vdc input and the outputstage is what ever you select

spuffock · 5th August 2004, 11:29 PM

100nF capacitors are good for this sort of problem. One across the motor brushes is my best bet. Next try one across the PIC power pins. Also check that no PIC pins are programmed as inputs and left floating.

2camjohn · 6th August 2004, 03:25 PM

TillEulenspiege:
Thanks I will try that circuit now.

spuffock:
There is already a capacitor accross the motor brushes of the motor, but the old motor (which worked perfectly) did not have one.

I will try putting a capacitor across the pics power rail.

I only have 10nf, will that produce the same effect?

Thanks to all who have helped so far

M3S90 · 6th August 2004, 05:22 PM

Try a 2k pull down resistor between the pic and the 1k resistor.

TillEulenspiegel · 7th August 2004, 02:35 AM

Quote:

Originally Posted by M3S90

Try a 2k pull down resistor between the pic and the 1k resistor.

Yup That was my first inclination. IIRC the PIC I/Os are tri-state which means they float unless active. Don't know the logic convention I think it's active on ( Pos logic ). Don't use a 2k tho use a 10k after the 1k.

Exo · 7th August 2004, 09:30 AM

you don't need a pull down on a pic...
if the pin is declared an output it can source AND sink....

if the pin is floating then he made a software error...

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5th August 2004, 07:15 PM	(permalink)
2camjohn	Cheers dude, But I have a small optocoupler here http://www.optocomponents.com/Quicklist4/SFH618A-2.htm Could i use this with a couple of transistors to produce the results I want (Switching 2A @ 9V with a signal of 6V) Thanks __________________ The first rule of mstechca club is do not talk about mstechca club. http://www.electro-tech-online.com/s...induser&u=1245

5th August 2004, 10:42 PM	(permalink)
TillEulenspiegel	Yes if you want , I'd use a TIP120, It's a darlington pair in a to-220 case ( sorry American convention) , but there are solid state relays that will do the job and all they need is a 3-30vdc input and the outputstage is what ever you select

5th August 2004, 11:29 PM	(permalink)
spuffock	100nF capacitors are good for this sort of problem. One across the motor brushes is my best bet. Next try one across the PIC power pins. Also check that no PIC pins are programmed as inputs and left floating.

6th August 2004, 03:25 PM	(permalink)
2camjohn	TillEulenspiege: Thanks I will try that circuit now. spuffock: There is already a capacitor accross the motor brushes of the motor, but the old motor (which worked perfectly) did not have one. I will try putting a capacitor across the pics power rail. I only have 10nf, will that produce the same effect? Thanks to all who have helped so far __________________ The first rule of mstechca club is do not talk about mstechca club. http://www.electro-tech-online.com/s...induser&u=1245

6th August 2004, 05:22 PM	(permalink)
M3S90	Try a 2k pull down resistor between the pic and the 1k resistor.

7th August 2004, 09:30 AM	(permalink)
Exo	you don't need a pull down on a pic... if the pin is declared an output it can source AND sink.... if the pin is floating then he made a software error...