Transistor Damage - Needs protection

[spec]

Hey all.

I have rebuilt the cct, but when switching SW10, it switches the relay as expected, but when I open SW10, it doesn't switch off. Could the protection I added and changing the resistance value to 1k have caused this?

Jason

Hi Hjb,

I just had a quick look at your schematic of post #13.

The 5V line, '5V Drive for MicroProcessor CN3-2B does not appear to connect to any part of the circuit.

According to my analysis, once SW10 is made the relay wiper will close and Reg 2 will produces 5V at its output.

Thus, if SW3 and SW7 are made, Q1 will be conduct and will hold the relay on.

The circuit looks rather complex- would you like to post an itemized list of what functions you would like. For example, it is possible that the relay cold be eliminated as far as I can tell.

spec

 

[Huttojb1]

Thanks Spec, if you look at the attachment PoerSuppy3, if I switch SW10 the relay closes, if I open SW10 the relay opens.

If I close SW10 the relay closes, then SW7 holds the relay closes and SW10 can be release without the relay opening. When sw7 is opened the relay opens.

This worked ok until I made the changes suggested, apart from the transistor being damage. But now when I switch SW10 and open it again the relay stays closed.

I don't understand why?

Jason.

 

[spec]

Thanks Spec, if you look at the attachment PoerSuppy3, if I switch SW10 the relay closes, if I open SW10 the relay opens.

If I close SW10 the relay closes, then SW7 holds the relay closes and SW10 can be release without the relay opening. When sw7 is opened the relay opens.

This worked ok until I made the changes suggested, apart from the transistor being damage. But now when I switch SW10 and open it again the relay stays closed.

I don't understand why?

Jason.

Just to clarify,
(1) SW7 is open
(2) When you close SW10 the relay closes
(3) When you open SW10 (with SW7 still open) the relay remains closed.

Is that correct?

spec

 

[MikeMl]

Post the schematic again, with the values as they are now. What position are all the switches when the relay should open but doesn't?

Are you asking us to check that your pcb layout matches the schematic (LVS)?

 

[Huttojb1]

Just to clarify,
(1) SW7 is open
(2) When you close SW10 the relay closes
(3) When you open SW10 (with SW7 still open) the relay remains closed.

Is that correct?

spec

Yes Spec, this is correct!!

Post the schematic again, with the values as they are now. What position are all the switches when the relay should open but doesn't?

Are you asking us to check that your pcb layout matches the schematic (LVS)?

Hey mike, not asking you to check the pcb, already done that a million times, just posted it just in case. I'll post the schematics when I get home today.

 

[spec]

Hi Hjb,

Going by your post #13 schematic, I can find no reason why the relay should stay energized.

spec

 

[Huttojb1]

Hi Hjb,

Going by your post #13 schematic, I can find no reason why the relay should stay energized.

spec

Thanks Spec,

I'm hoping it's something wrong with my cct, I'll retrace the tracks to ensure it matches the design. I'll let you know

Thanks again to you both for helping.

Jason

 

[Huttojb1]

Thanks Spec and Mike, I have managed to retrace the cct and guess what....!!! one of the transistors was in the incorrect orinitation, i have rotated the transistor round and all working again. Thank you

 

[spec]

Thanks Spec and Mike, I have managed to retrace the cct and guess what....!!! one of the transistors was in the incorrect orinitation, i have rotated the transistor round and all working again. Thank you

Well done- it is very rare that a circuit works first time.

spec

 

[Huttojb1]

Gents,

Just want to say thank you for your help on this matter. I created the PCB and fitted and so far so good.