inexpensive timing relay circuit

Thread Starter

strpdbas

Joined Dec 24, 2008
99
Q4 was the problem. I had confirmed the values of all resistors prior to installing them. As soon as I removed Q4 the gate voltage went to 0V. I installed a new Q4 and all is good. How sensitive are they to heat? should I use a heat sink when soldering them?
 

eblc1388

Joined Nov 28, 2008
1,542
Q4 was the problem. I had confirmed the values of all resistors prior to installing them. As soon as I removed Q4 the gate voltage went to 0V. I installed a new Q4 and all is good. How sensitive are they to heat? should I use a heat sink when soldering them?
Q4 is not particular sensitive to soldering but does not like static electricity. You could have damaged it by rough handling instead of prolonged soldering. If your body is electrically charged and you touch the gate pin, then it could be damaged. They are ok once installed into the circuit board.

Is your prototype now working as it should? i.e. one press of the limit switch would stop the motor for a few seconds and then the motor goes in the other direction?
 

Thread Starter

strpdbas

Joined Dec 24, 2008
99
Yes, holding the switch closed no longer causes the motor to instantly reverses. I am going to install the 470uF C4 cap. in the next board, I would like to increase the delay time closer to 1 minute. The board now seems to be in order. I will let you know the results of the next board. Thank you for all of your help.
 

eblc1388

Joined Nov 28, 2008
1,542
Another way to change the 555 timing is to use a 470K VR for R3 and change the series resistor R1 from 22K into 220K.

This will give an adjustable timing range of 24~76 seconds, using the same C4 100uF capacitor.

Or you can use a 1MΩ variable resistor with the same R1 22K resistor to get a range of 2~112 seconds, also using the same 100uF C4 capacitor.
 

Thread Starter

strpdbas

Joined Dec 24, 2008
99
I had gone to the website you had suggested, Electronics Lab, and used the monostable timeout calculator to come up with the 470uF cap as I was looking to get a max. delay of about 1 minute. The calculated maximum delay with the 470uF is about 52 seconds, although I am not sure what the minimum delay would be. I have certainly learned a lot with your help!
 

Thread Starter

strpdbas

Joined Dec 24, 2008
99
I should not have spoken so soon. I made a second board incorporating all of the changes. It started out OK but stopped working. I measured both the AC and DC output of the transformer and measured only 3.4VAC & DC. I removed the transformer from the board and wired it directly to 110VAC soldered the jumpers to get 10VAC output. I plugged the tx in and measured the correct 10V. Upon reinstalling the tx on the board the output again dropped to 3.4V. There are no breaks in the foil. I tested continuity at all terminals. I am beginning to think I should take up golf!!
Could a bad bridge rectifier or C5 cause the problem?
 

eblc1388

Joined Nov 28, 2008
1,542
lthough I am not sure what the minimum delay would be.
If you put in the value of the series resistor R1 22K into the calculator, that will give you the minimum delay time. The total timing with a certain capacitor depends on the value of (R1+VR) so if VR=0, i.e. when you set it to minimum, then net resistance value =R1.

Upon reinstalling the tx on the board the output again dropped to 3.4V. There are no breaks in the foil. I tested continuity at all terminals.
Let it sit there at 3.4V for 10 seconds. Then remove AC power. Use your hand to feel over the CD4013B and the 555. Does anyone get hot to the touch?

If so remove it from the socket and watch your voltage return to 14V.

I am beginning to think I should take up golf!!
Try tell others how to play golf using a forum. :)

Could a bad bridge rectifier or C5 cause the problem?
Anything is possible. The aim is to isolate the fault and rectify it.
 
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Thread Starter

strpdbas

Joined Dec 24, 2008
99
You must have been responding to me while I was sending an additional reply to you. It makes sense regarding the 555 timer. With the 470uF cap. and the 22K resistor the minimum time comes back at 11.3 seconds.
I hope you have a simple answer to my current problem. I was very carefull in handling all components, and made sure to examine all solder joints for cold joints and shorts before powering up the board. Fortunately a 3 x 4 inch board is large enough to allow for pretty wide traces, and good spacing between tracks.
 

Thread Starter

strpdbas

Joined Dec 24, 2008
99
After unplugging the board the 4013 was too hot to touch. I removed the 555 and 4013 plugged back in and voltage was then correct. I unplugged board and installed new 555 & 4013. Plugged back in. Voltage is now correct, but limit switches do nothing. Motor runs in one direction. Could something else have been fried because of the 4013? I do not hear the relays at all. I left the unit plugged in and neither chip even got warm to the touch.
 

eblc1388

Joined Nov 28, 2008
1,542
Plugged back in. Voltage is now correct, but limit switches do nothing. Motor runs in one direction. Could something else have been fried because of the 4013? I do not hear the relays at all. I left the unit plugged in and neither chip even got warm to the touch.
Anything is possible.

Please repeat the 18 voltage tests earlier. If the result of the test is the same, no need to post result. Replace Q4 and check your "new circuit board" copper trace as per circuit diagram. You may have incorrect copper trace(s) connecting power into the IC output pins.
 

Thread Starter

strpdbas

Joined Dec 24, 2008
99
The board layout I made has been used in both boards. The only changes I made were the components you suggested and connecting the third terminal of the potentiometer. The reason I had attached a drawing of the board layout was I was hoping you would confirm proper layout. I will do the voltage tests again, but would appreciate it if you could confirm whether or not my layout is correct.
MASTERCKT..jpg
 

eblc1388

Joined Nov 28, 2008
1,542
Your low voltage circuit trace matches the schematic diagram.

However, there are important design consideration with regard to the proximity of AC line voltage copper trace close to the low voltage circuit trace. This is real bad and could potentially damage your circuit and causes flashover. This might also explain why your circuit get damaged unexpectedly.

Thus I have put in a grounded trace barrier on your board. This trace extends from the bottom to the top and connects both to the AC power ground and the low voltage 0V. The trace separation of those AC signals to this grounded trace are not sufficient at the moment. You still need to try to move all the circuit traces that carry AC signals on the right side of this grounded trace as far to the right and away from this trace as possible.
 

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Thread Starter

strpdbas

Joined Dec 24, 2008
99
I have redesigned the entire layout to maximize line and low voltage track separation. Per your instruction I have incorporated common trace between ac grnd. to 0vdc. Please review the new design and let me know if I missed anything. I will wait for your response before starting a new board.

NEWBOARD.jpg
 

eblc1388

Joined Nov 28, 2008
1,542
Yes it is much better.

I offer my slight modified version to yours to put a grounded trace between low voltage and high voltages. I moved the 0.68uF and there are some cosmetic changes too.

 

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Thread Starter

strpdbas

Joined Dec 24, 2008
99
SUCCESS!!! Working perfectly. The only mod I would like to make regards the time delay. With your OK I would like to use a 200K trimpot and a 2.2K for R2, and C4 @ 330uF. Based on the 555 calc. this combination should give me a min. 8 sec. delay and a 73 sec. max. delay. I'm glad I finally got you to look at my board layout as it was becoming frustrating each time one got fried.
 

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eblc1388

Joined Nov 28, 2008
1,542
SUCCESS!!! Working perfectly.
I see that you have left out the jumper that I added between the -Ve of the bridge rectifier and the capacitor -Ve.

This is the subtle change that I was referring in the previous post. Don't do that.

You may think the circuit is OK but it is not.

Why would you need an extra jumper for R4 330KΩ?

You should also consider adding 4 holes in each corner of the PCB for mounting purposes but this is a trivial point.

I would like to use a 200K trimpot and a 2.2K for R2, and C4 @ 330uF. Based on the 555 calc. this combination should give me a min. 8 sec. delay and a 73 sec. max. delay.
Yes, you can use these values for the RC timing.
 

Thread Starter

strpdbas

Joined Dec 24, 2008
99
I see what you mean regarding R4, but I am missing the jumper you say I left out. I thought I followed your instruction correctly. I will drill holes in the corners when I fit the board into the enclosure.
 
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