PNP transistor issues

Ron H

Joined Apr 14, 2005
7,063
Dumb question: Do you have ALL the grounds connected together, and pin 16 connected to +12V, as shown in the attached schematic?
 

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abcinc

Joined Apr 29, 2009
26
yes all the grounds are connected to the negitive wire on the power supply. Also, the 4060B works perfectly. The issue is, the relay does not turn off when the 4060B pin goes high.
Thanks everyone.

Dave
 

Ron H

Joined Apr 14, 2005
7,063
I think you have the collector and emitter swapped. The b-e junction will break down, causing exactly the symptoms you mentioned in your first post: With the base connected to +12V, or disconnected, the "collector" voltage will be around 3 to 6V, due to the b-e breakdown.
 

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abcinc

Joined Apr 29, 2009
26
OK, I will try to swap them (e and c) and see what happen. Then I will repost in a few hours. However, I did previously check the datasheet against the diagram a few times so I don't think they are backwards but I will reverse them.

Thanks again.

Dave
 

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abcinc

Joined Apr 29, 2009
26
Hi all, I swapped e anc c. Now the coil has 12 volts when circuit is turned in and the output from the relay is zero volts. I believe I had e and c correct previously. After the 15 minutes, the pin on the 4060B goes high and the relay turns off and the relay output is 12.24 volts. This is exactly what I want but in reverse

Any other ideas?

Thanks

Dave
 
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Ron H

Joined Apr 14, 2005
7,063
Hi all, I swapped e anc c. Now the coil has 12 volts when circuit is turned in and the output from the relay is zero volts. I believe I had e and c correct previously. After the 15 minutes, the pin on the 4060B goes high and the relay turns off and the relay output is 12.24 volts. This is exactly what I want but in reverse

Any other ideas?

Thanks

Dave
It sounds like the relay is now doing what it was designed to do. Does the collector voltage go to zero (relative to GND) after 15 minutes? If so, it is working correctly. If you have a double-throw relay (SPDT or DPDT), use the other set of contacts.
I looked over the entire project site, and there were 2 options. The other one used an NPN to drive the relay. This inverts the relay action, but the designer had specified a double-throw relay, so you could use either circuit.

If you have a siingle throw relay, you can use the PNP as an emitter follower, or use the NPN version, to get the relay to have the inverted function.
 

Thread Starter

abcinc

Joined Apr 29, 2009
26
The c (previously e) goes to zero after the 15 minutes when pin 13 on the 4060B goes high. The R56 is a SPDT. I don't understand why when c and e were the other way around it did not work at all. Now it works but backwards. I know the other diagram used an npn. maybe Ron got it backwards. Should I get an npn? If so, which way to connect? What to base and what to e and what to c?

Thanks

Dave:):)
 

Ron H

Joined Apr 14, 2005
7,063
The c (previously e) goes to zero after the 15 minutes when pin 13 on the 4060B goes high. The R56 is a SPDT. I don't understand why when c and e were the other way around it did not work at all. Now it works but backwards. I know the other diagram used an npn. maybe Ron got it backwards. Should I get an npn? If so, which way to connect? What to base and what to e and what to c?

Thanks

Dave:):)
When you say Ron, I assume you mean the guy that designed the circuit. My name is also Ron.

It does not work backward. It did not work at all before because C and E were swapped.

Do you understand that you can use the other relay contact?

If you really want to use an NPN, look at circuit 1 on the top of the page you linked to. The one you built is circuit 2.
 

Ron H

Joined Apr 14, 2005
7,063
As Ron the designer said, choice of NPN or PNP depends on whether you want the relay on after the timeout, or off after the timeout, respectively. This is a power dissipation or battery life issue, and it all depends on how you are going to use it.
 

Thread Starter

abcinc

Joined Apr 29, 2009
26
Hi, I changed it to an NPN. Put e to Vin, C to pin 2 of relay (coil) and b to the 780 ohm resistor. Now the relay output is 12.24 volts when circuit is turned on and after 15 minutes the relay output is zero. Just the way I wanted. Thanks for your help. I believe Ron J should have used a pnp on circuit 1 and npn on circuit 2. However I have 1 additional issue. After a few minutes of relay output off (past the 15 minutes) the output becomes 12.24 volts again. Even though the 12 volts are still on the coil. I think I may have damaged it some or the current comming through the NPN is not enough to keep it clamped. The R56 -5.5-12 has only 1 coil and 1 contact so I am not sure what you mean by other contact.

Thanks Ron

Dave
 

Ron H

Joined Apr 14, 2005
7,063
Hi, I changed it to an NPN. Put e to Vin, C to pin 2 of relay (coil) and b to the 780 ohm resistor. Now the relay output is 12.24 volts when circuit is turned on and after 15 minutes the relay output is zero. Just the way I wanted. Thanks for your help. I believe Ron J should have used a pnp on circuit 1 and npn on circuit 2. However I have 1 additional issue. After a few minutes of relay output off (past the 15 minutes) the output becomes 12.24 volts again. Even though the 12 volts are still on the coil. I think I may have damaged it some or the current comming through the NPN is not enough to keep it clamped. The R56 -5.5-12 has only 1 coil and 1 contact so I am not sure what you mean by other contact.

Thanks Ron

Dave
Your NPN connection is incorrect. As I said, look at Ron's circuit number 1. See below.
And Ron didn't get anything backward. On this page, beside the circuit 1 schematic, there is a scrolling description of how both circuits work. he describes how both NPN and PNP work, and he is correct.
 

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abcinc

Joined Apr 29, 2009
26
Hi Ron, circuit 1 has e connected to ground I am not switching ground. I am switching 12 V. Should I have C connected to 12V, e connected to coil and b connected to the resistor from 4060b?

I looked at the description a little more. Maybe I bought the wrong relay. This relay has the output on unless power is supplied to the coil. Ron J's description says the transistor should turn off and then relay goes off cutting the output.
Thanks again.

I think I can use this relay with an NPN. How should the connections be?

Thanks so much.

Dave
 
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Ron H

Joined Apr 14, 2005
7,063
You said your relay is SPDT. Is it an NTE R56-5D.5-12? If so, it has a normally closed contact, and a normally open contact.
 

Thread Starter

abcinc

Joined Apr 29, 2009
26
Hi Ron, circuit 1 has e connected to ground I am not switching ground. I am switching 12 V. Should I have C connected to 12V, e connected to coil and b connected to the resistor from 4060b?

I looked at the description a little more. Maybe I bought the wrong relay. This relay has the output on unless power is supplied to the coil. Ron J's description says the transistor should turn off and then relay goes off cutting the output.
Thanks again.


I see, pin 7 is normally open. So use the PNP with e to Vin, and c to pin 2 (coil) and out put to pin 7?

Thanks again.
Dave
 
I will second the fact that both Ron and Ron H are correct. Your circuit might work for a few minutes and then stop because the transistor is probably giving up due the way it is connected in your circuit.

The diagram of the transistors located on your schematic pages are not necessarily correct for the transistors you are using. As a matter of fact, for the PNP you used the diagram has the collector and emitter switched, just as Ron H suggested.
 

Ron H

Joined Apr 14, 2005
7,063
Hi Ron, circuit 1 has e connected to ground I am not switching ground. I am switching 12 V. Should I have C connected to 12V, e connected to coil and b connected to the resistor from 4060b?

I looked at the description a little more. Maybe I bought the wrong relay. This relay has the output on unless power is supplied to the coil. Ron J's description says the transistor should turn off and then relay goes off cutting the output.
Thanks again.


I see, pin 7 is normally open. So use the PNP with e to Vin, and c to pin 2 (coil) and out put to pin 7?

Thanks again.
Dave
I'm not sure what you have until you answer my questions:
Does it have the pinout shown below?
 

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abcinc

Joined Apr 29, 2009
26
Yes, that pin out. Currently I have the NPN with c connected to pin 2. Vin connected to pin 1 and ouput connected to pin 14. If using PNP, then should I connect e to Vin, c to pin 2, b to resistor R7 , and Vin to pin 7 on the R56?

Thanks Ron
 

Ron H

Joined Apr 14, 2005
7,063
Yes, that pin out. Currently I have the NPN with c connected to pin 2. Vin connected to pin 1 and ouput connected to pin 14. If using PNP, then should I connect e to Vin, c to pin 2, b to resistor R7 , and Vin to pin 7 on the R56?

Thanks Ron
No, that's not right.
In your original circuit with the PNP, you said the relay was doing just the opposite of what you wanted. Which contact pin did you use for Vin (+12V), and which one for Vout?
 
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