inexpensive timing relay circuit

eblc1388

Joined Nov 28, 2008
1,542
I meant to ask you why does the motor use such a large capacitor? It is rated .68uF @ 400v. Is there another value I could use to save on space and cost?
0.68uF is a small value capacitor for usage on AC motor. You have to stick with this one as capacitance and voltage is determined by the physical motor. One can't reduce either the value or the voltage of the capacitor.

After getting more information from your various attempts in building the circuit, I have re-examined the circuit design but see no other possible problem leading to component failure. It would be beneficial to use a lower voltage of 6V or 9V but even at 15V, the circuit should not get damaged.

Let's wait until you have got the proper 2N7000 and fitted them to see if there are more problems. It could help if you can connect "LED with series resistor(2KΩ)" across each relay coil temporarily to see how the relay operates. Do not connect the motor at first before you check that the circuit function is correct. A malfunction circuit would attempt to change the direction of the motor before switching off the power first and this could lead to the damage of various component.

If the circuit functions OK without the motor but fails soon after connecting the motor then there would be a different approach to correct the problem.
 

Thread Starter

strpdbas

Joined Dec 24, 2008
99
OK, I will stop by the local Radio Shack store and purchase some LED's and place one in series with a 2K resistor across each of the relay coil contacts. I assume this is to visually determine if the relay sequence is operating correctly. Would it be advisable to also increase the value of R4 to 1MegOhm? I did find 9V tx I can use, I assume I would still use the 12v relays with the 9v tx. I will report back as soon as I have results,
 

eblc1388

Joined Nov 28, 2008
1,542
OK, I will stop by the local Radio Shack store and purchase some LED's and place one in series with a 2K resistor across each of the relay coil contacts. I assume this is to visually determine if the relay sequence is operating correctly.
Yes. The LED will tell you if the operation is correct. You can buy 1.8K or 2.2K resistor if 2K is not available. It does not matter.

Would it be advisable to also increase the value of R4 to 1MegOhm?
Yes. You can also increase the capacitor at the 2N7000's gate from 0.1uF to 0.2uF. This will give you more elapse time before motor direction connection is changed after power to it is switched out via relay. It also make the LED lights up sequence easily visible.

I did find 9V tx I can use, I assume I would still use the 12v relays with the 9v tx. I will report back as soon as I have results,
Yes. The rectified voltage would be about 12V and the transformer will put out more than 9V AC anyway.

Here is what to test for the correct function in the next completed PCB:

1. AC power ON, limit switches connected but no motor connection.

2. The LED at the 555 output relay should be OFF.

3. Press limit switch, the LED at 555's output will light immediately, then follows by a change on the other LED(the change can either be On->Off or Off->On) on the motor direction change relay. You have to confirm that these two LEDs event occur one after another but not simultaneously. The time delay between these two events should be short but noticeable. This time is controlled by R4 and capacitor, not by the 555.

4. When the 555 output LED goes OFF, press another limit switch and the operation in 3 above will repeat.

5. Let the circuit stand for while and then press the limit switches many times and confirm each time the correct operation results. Power OFF and ON again after 30 seconds repeatedly to check that the circuit still works OK.

6. Now connects the motor leads and check operation as in (3) again.
 

Thread Starter

strpdbas

Joined Dec 24, 2008
99
OK, I removed the 330k resistor from pin 1 of 4013 and replaced with a 1 megohm. I put 2 new 2n7000, new 4013, and new 555, 2 new relays. I installed one LED in series with a 22.1k resistor across the top of each of the diodes d3 and d4 . I soldered anode of LED to anode of 1n4001 and cathode (flat edge) of LED to cathode (banded end of 1n4013). I unsoldered the black and red motor leads. As soon as I plug the unit in neither LED illuminates. I measured voltage @ relay terminals as follows:
Relay 1 coil activated as I measure 118vac @ the NO contact. Relay 1 coil never de-energises. When I press limit switch 2 relay 2 coil activates closing the contacts to the NO and com. When I press switch 1 the relay de-energises closing the NC and com. The LED's never came on. It seems like the switches are doing what they are supposed to but the 555 timing circuit is not operating correctly. I am beginning to wonder if my solder iron is too powerful. What would you recommend as a good iron? AHHHHHH!!!!!!!
 

eblc1388

Joined Nov 28, 2008
1,542
I installed one LED in series with a 22.1k resistor across the top of each of the diodes d3 and d4 . I soldered anode of LED to anode of 1n4001 and cathode (flat edge) of LED to cathode (banded end of 1n4013).
The value of the resistor is too high. You will need a resistor between 1K~2K2 for the LED to light.

One end of the LED is connected only to this resistor. So you are left with a free end on the LED and a free end on the resistor. Like this:

end A---/\/\/\----|>|------ end B

The LEDs need to be connected in opposite direction to the 1N4001 diodes(i.e. end A to +Vcc and end B to 2N7000 DRAIN) because in normal use, the 1N4001 diodes are reverse biased and never conducts.

For the 555 output LED, end A to pin#3 and end B to 0V.
 

Thread Starter

strpdbas

Joined Dec 24, 2008
99
OK removed 22k replaced w/2.2k. LED cathode to d4 anode. LED anode to one leg of 2.2k. Other leg of 2.2k to d4 cathode. Same done for d3. Plugged in, rly 1 energizes (LED on) rly2 off. Timed over two minutes, rly 1 still energized. Press sw1, rly 1 on, rly 2 on. Pressed sw2, LED gets dim, not off, rly 1 still on. Press sw 1 again, rly 2 LED goes from dim back to normal. Rly 1 never went off. Unplugged unit waited a minute or so, plugged back in now both relay LED's go on.
 

eblc1388

Joined Nov 28, 2008
1,542
Timed over two minutes, rly 1 still energized.
It is confusing to refer them as relay1 or 2. Let's from now on refer them as 555relay and 4013relay.

When first power ON, the 555relay should be off or go off in 60 seconds.

If your 555relay stays on for over two minutes, then the 555 circuit is faulty. Check that pin#2 is at +Vcc. If not, then the 2N7000 connected to Pin#2 is faulty.
 

Thread Starter

strpdbas

Joined Dec 24, 2008
99
OK I will also refer to 2n7000 as 555 Q & 4013 Q.
Power on, both LED on. P2 voltage of 555 1-2volts (bounces around alot).
Neither LED went off. During this time I measured 4013 Q G=4.8. D= 0.1.
555 Q G=0.02, D=10.6. Had power on for at least 3-4 minutes and both LED on entire time.
 

eblc1388

Joined Nov 28, 2008
1,542
OK I will also refer to 2n7000 as 555 Q & 4013 Q.
Power on, both LED on. P2 voltage of 555 1-2volts (bounces around alot).
Neither LED went off. During this time I measured 4013 Q G=4.8. D= 0.1.
555 Q G=0.02, D=10.6. Had power on for at least 3-4 minutes and both LED on entire time.
Your voltage measurement is way off. The above three readings are wrong.

Are you using a analoge voltmeter or a Digital one?
 

Thread Starter

strpdbas

Joined Dec 24, 2008
99
Digital. I took measurements this am. It is odd that sometimes when plug in, both LED on, sometimes only 555 LED on. 555 LED never goes off. Also 4013 LED sometimes goes dim when close sw2. Today it flickers, or goes dim.
Measurements w/digital multimeter as follows:
Power on, no switches depressed.
4013 P1=0.0 P14=14.7
4013Q G=2.0 D=13.9
555 P2=1.0
555Q G=0.5 D=11.4

SWITCH 1 DEPRESSED
BOTH LED ON
4013 P1=13.7 P14=13.7
4013Q G=8.9 D=0.08
555 P2=1.1
555Q G=.03 D=10.7

SWITCH 2 DEPRESSED
BOTH LED ON (4013 FLICKERING)
4013 P1=0.0 P14=14.5
4013Q G=2.3 D=10.9
555 P2=0.95
555Q G=0.03 D=11.5

The earth ground of 115ac is soldered to the ground trace of board.
I also included the board layout if it helps.
newboard.jpg
 

eblc1388

Joined Nov 28, 2008
1,542
Digital. I took measurements this am. It is odd that sometimes when plug in, both LED on, sometimes only 555 LED on. 555 LED never goes off. Also 4013 LED sometimes goes dim when close sw2. Today it flickers, or goes dim.
Now things get interesting.

To troubleshoot this mess, you will need to:

a. see extra info added at bottom of this post
b. test if thing goes back to normal. if not,
c. unsolder and remove the 2N7000 connected via capacitor to pin#2 of 555.
d. remove the 4013 from socket

This will let you isolate the two sections of the circuit.

Power On, let the board sit idle for a few minutes, then make these voltage measurement:

1. 555 pin#2 and pin#3 voltage, is the 555Led on or off?

2. gate voltage of the remaining 2N7000(the 4013 one), is the 4013LED on of off?

3. plug in and switch on your soldering iron. Set your DVM to AC voltage, with one meter lead to ground and the other touch the soldering iron tip. Can you measure a large AC voltage? What is the voltage?

4. Have you ever soldered anything on the PCB with the PCB power supply ON?

Added: Use a sharp object to clean the stuff left over from soldering between the pins of IC socket and semiconductor pads. Runs the object several times between the gaps to make sure no dirt is leftover. Then clean the board soldering side with alcohol and blow it dry for a few minutes until the board is hot to the touch. Let it cool down and do the above test.
 
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Thread Starter

strpdbas

Joined Dec 24, 2008
99
555Q removed, 4013 removed. Plug in both LED on.
555 P2= 4.0 P3 = 12.6 LED on.
4013 Q Gate=2.56 LED on.
Ground to solder gun tip 60vac.
No soldering with power on.
 

Thread Starter

strpdbas

Joined Dec 24, 2008
99
The good news is I received my new 2N7000's today. I will get a solder iron with ground leg. Also the one I am using is 60W. I will start fresh tomorrow and post results.
Would you suggest a method for me to test as I assemble. This way I can isolate problems before they become compunded. I hope this makes sense.
 

SgtWookie

Joined Jul 17, 2007
22,230
Do not use a "solder gun" on such projects, as you will most likely "zap" your parts much more quickly than you can say "dang!". :(

A 20W to 30W pencil tip iron is adequate for most projects, if you're using 63/37 or 60/40 solder. 63/37 is preferable, as it is eutectic; it does not have a "plastic" state - but it's getting harder to obtain. Eurofolks are probably limited to RoHS compliant solder, which can require a great deal more heat.
 

Thread Starter

strpdbas

Joined Dec 24, 2008
99
Wer'e almost neighbors. I am orig. from NY but now live in Oldsmar. I am using a 60W pencil. I guess a 25W 3 wire unit should be OK. Boy getting this prototype to work has been a real P.I.M.A_ _!! As far as the solder goes I have a 5# roll my father gave me 20 years ago.
 

Thread Starter

strpdbas

Joined Dec 24, 2008
99
OK started fresh, new components, different 2N7000's, they came yesterday, and a new grounded 15w pencil. 0V @ tip. Cleaned bottom of board w/alcohol.
Took four sets of measurements, 2 CW (SW1) and 2 CCW (SW2).
First time powering up motor start was delayed. In all subsequent tests motor started immediately when powering up. The motor ran both CW on power up and CCW on power up. These are the measurements:

1st power up-motor off, started after 11 sec. running CW.
4013 P1 = 14.96 P4 = 0 P6 = 0 P14 = 14.9
4013Q G = 14.4 D = 0.7
555 P2 = 14.73
555Q G = 0 D = 14.26
Pressed SW2 motor stops, 10 sec delay, started CCW
4013 P1 = 0 p4 = 0 p6 = 0 p14 = 16
4013Q G = .08 D = 16
555 P2 = 15.83
555Q G = 0 D = 15.38
2nd test power on motor on running CCW.
3rd test power on motor on running CW.
All 4 test measurements were same as above, give or take .1v.
The switches are working correctly, the voltages seem right.
One problem I am having is the delay adjustment. I tried 100uF w/22k,
330uF w/22k, and a 470uF w/22k. The potentiometer has no effect on the delay. No matter which combo I used the delay is never more than 3-4 seconds (other than in the initial power up) and the pot does nothing. I removed pot cheked out OK @ 104K.
I then replaced C4 with the next higher value but nothing worked. I also put another 555 in but to no avail.
I measured the AC @ the Red & Black motor leads. It was interesting to note that the voltage was 154.5vac on the running leg and 118vac on the non running leg. I guess the motor cap is the reason.
 

eblc1388

Joined Nov 28, 2008
1,542
One problem I am having is the delay adjustment. I tried 100uF w/22k,
330uF w/22k, and a 470uF w/22k. The potentiometer has no effect on the delay. No matter which combo I used the delay is never more than 3-4 seconds (other than in the initial power up) and the pot does nothing. I removed pot cheked out OK @ 104K.
I then replaced C4 with the next higher value but nothing worked. I also put another 555 in but to no avail.
I'm glad you have gotten most of the hurdles behind. That's a good start.

A 555 monostable with shortened timing and not adjustable by changing series resistor. This is a very hard one to crack.

Place a DVM on the capacitor C4 and watch what happens during the delay period. The voltage should rise steadily from 0V to 10V before the motor run again. When the motor runs, the capacitor has zero volt. Press limit switch, motor stops and capacitor charges up. Does the capacitor charges up to 10V within 5 seconds?

Post back what you see regarding to the behaviour of this voltage rise.
 

Thread Starter

strpdbas

Joined Dec 24, 2008
99
When I plugged unit in motor starts turning. Measure .2v @ C4. Pressed limit switch, voltage went up to 9v in ~2 sec. and then motor runs again.
I took these measurements with the 100uF cap installed
 
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