[SOLVED] Changing/switching Polarity

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me_guitarist

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Hello guys!

I have successfully reverse the output polarity to my magnet coil marked 'Coil(+), Coil (-)' with DPDT relay to reverse the North & South pole so when power removed the magnet will release with sourcing current from C1, R1 prevent power ON surge.

I'm wondering how can I done this with transistor?
Will this circuit also provide back EMF?

Pls see attached photo & advise me.
 

Dear me_guitarist
Hi
Would you like to change your relay with transistor or do you want to control your relay with transistor ?
Best Wishes
Goldsmith
 

Dear Goldsmith,
Thanks for yr repky.

I'll like to replace the relay with NPN transistor. My coil consume 100mA max. So I think some 2N2222 or 2N4401 will do the job.
 

It is pretty simple .
But before helping with transistor , tell , me , please , is it important to you , to use transistor ? why not opto couplers ( there are many opto couplers that consists totem pole at the out put , to provide high currents ! )
Best Wishes
Goldsmith
 


Dear Goldsmith.

I prefer transistor as I have it now. Its better to have opto to handle higher current when I move to a higher coil I wont need to change the components.

Tks!

---------- Post added at 14:25 ---------- Previous post was at 12:29 ----------

I need to reverse the output using C1's storage when power is removed.

Anybody have any idea to replace the relay with NPN transistor?
 

Hi again
You can use two transistor instead of each contact simple that will work at class B CE amplifier .
Best Wishes
Goldsmith
 

Dear Goldsmith,

Thanks for yr reply.
Can you pls explain more details or any example I can look into?

Thanks!
 

Dear me_guitarist
Hi
Sure , but before that , what are + coil and - coil ? i'm a bit confused with your circuit .
Best Things
Goldsmith
 

Hi Goldsmith,

The C+& C- connect to a non polarised electro magnet which I have to reverse its polarity to release using current that stored in C1 when power removed.

Thanks!
 

As i understood , you want change the polarity across the coil ? if yes , you can use an H bridge with 4 transistor that two of them are PNP and and another two , are NPN .
Best Wishes
Goldsmith
 

how to reverse the coil polarity when power removed?
 

Dear Goldsmith,

pls look at my circuit again.
When the power applied, the relay coil energised.
NO closed contact, C1 charged thru R1.

When power removed contact open, C1 supply the magnet with reverse polarity (NC contact)just enough power to release a metal plate which attached to the magnet when power applied.
What I need is replace the relay with transistor will this possible & how?
 

Dear me_guitarist
Hi again
See below , please :

If you change v7 , to +15 volts , the voltage across the resistor will be reverse . ( remember , if you change v7 to +15 , you should change v9 to zero , and vice versa )
Best Wishes
Goldsmith
 

hi Goldsmith,

thanks for yr reply.

I dont have other power source rather than the main 24vdc. I cant figure out how to change the 0v to 15v or vize verse. Was the v7 & v8 replace with capacitor?
 

Hi again
It is an example . just you should know , supply voltage should be equal with V7 or V8 . ( if your supply is 24 m thus your V8 or V7 should be 24 volts too.
Good luck
Goldsmith
 

goldsmith said:
Hi again
It is an example . just you should know , supply voltage should be equal with V7 or V8 . ( if your supply is 24 m thus your V8 or V7 should be 24 volts too.
Good luck
Goldsmith
Click to expand...
Hi Goldsmith,

I just figure out the circuit. It works perfectly.
Kindly see attached schematic.

Any comments or advise are welcome.

Thanks!
 

Hi again
But why these high numbers of components ? because your load is inductive you can use a diode in parallel with the CE of each transistor , but another components are not important . because your frequency isn't high .
Best Wishes
Goldsmith
 

goldsmith said:
Hi again
But why these high numbers of components ? because your load is inductive you can use a diode in parallel with the CE of each transistor , but another components are not important . because your frequency isn't high .
Best Wishes
Goldsmith
Click to expand...
hi Goldsmith,

Thats the min. parts I can do.
Actually its not switching but reversing the output to the inductive load for a second of time which determine by the value of C1 when power removed.

---------- Post added at 12:55 ---------- Previous post was at 11:20 ----------

hi Goldsmith,

Will 1n4148 diode sufficient for the transistor CE junction?
thanks!
 

Will 1n4148 diode sufficient for the transistor CE junction?
thanks!
Click to expand...
Hi again
It depends on :
1- your maximum current
2- your maximum voltage
Best Lucks
Goldsmith
 

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