Thanks for the link!

Originally we had it connected directly to the 15V supply but like I said, my chips were burning up and after burning 4 of them I added the resistor to the power supply to step down the voltage. I don't think it was a factory reject because of so many of them having the same problem, unless of course, I have a knack for picking up rejected chips.

Does it matter that it is a CMOS version? The packaging said it was the same as the NE555??? We are in a small town without a good electrical supplier. That was the best I could find in short notice. But if the consensus is to change the chip then I will order the *right* one online. My boss is just in a hurry for this to be done if you know what I mean.

I purchased a 115VAC~15VDC converter that plugs directly into the wall.

 

Measure the 15VDC wall warts output. It's probably higher than you think if only a light load like the 555 is connected.

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Bill
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Now the low power Cmos 555 is trying to drive a base resistor for the transistor that is only 220 ohms. Why???
The 220 ohm resistor is trying to draw (15V - 0.7V)/220 ohms= 65mA but the low power Cmos 555 has a max output high current of only 10mA when its supply is 15V.

The solid state relay has an input current of only (15V - 1.3V)/1.5k ohms= 9.1mA so the transistor and its base resistor are not needed.
The solid state relay does not use an inductor so the diode across it is also not needed.

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Uncle $crooge

 

Are you referring to the output of the transformer? I measured that and it was about 15.4V DC

I actually don't have the transistor logic connected. I still have the first schematic I posted (see here)
Question RE: NE555 pulse generator

 

Bumping back to the top

 

hi DW,
Also bumping, that original circuit will still NOT work, sorry.

Have you modified the circuit in the way have suggested,?

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Eric " Good enough is Perfect "
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Thanks for the bump.

No the original circuit was not modified other than changing out the relay. According to Audioguru the transistor, base resistor, and diode are not needed.

 

OK,
So what stage and state is the project currently at.?
Do you require any more input from us.?

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I am still having the same problem with the voltage drop from the input to the output of the 555 chip when the relay is connected. The input is about 6.5V and the output is about 4V.

I guess I am still looking for ideas on how to correct this. It seems I am getting conflicting information regarding adding the transistor and diode circuitry. I have the transistor but don't want to solder it on until I am fairly sure that this will work.

 

That is normal. You have a 1k resistor in series with the power to the circuit so the supply voltage of the C555 is jumping up and down.
Also the Cmos 555 has a very low output current so it has a high output voltage loss.

Don't you still have a solid-state relay with a minimum input voltage of 3V?

__________________
Uncle $crooge

 

hi DW,
Look at this circuit.
The 100R and 12Vz will reduce the voltage to the NE555 to 12V

What is the electrical spec for the counter.??

Are you using a TLC555 CMOS or NE555 TTL

Attached Thumbnails

 

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Eric " Good enough is Perfect "
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Yes, but the output also goes to the timer/counter. The counter's input is 12V. And the problem is the counter isn't counting as it should because the input voltage is only 4V.

The 1K resistor was to step down the voltage because the 15.4V that comes from the transformer was too high for the chip and I kept burning them up.

Here is what I want to try now. (But it will have to wait until tomorrow for me to make yet another run to the store.) I want to take out the 1k Ohm resistor at the beginning of my circuit. And change the 15V power supply with a 12V power supply. I am hoping that the 12V power supply will be enough to run the circuit without blowing any more chips. I will let you guys know tomorrow how it turns out. In the mean time please feel free to offer any additional input or suggestions. Thanks again for all your help.

BTW, I am not a he as some of you referred to me earlier.

 

hi,
With a 12Vdc reg psu the 100R and12Vz are not required in my circuit.

Tell me the current rating of the counter, I know its 12V and we can use a transistor to drive it OK.?

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Eric " Good enough is Perfect "
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What is the 12Vz 0.5W symbol? Is that a voltage regulator?

The counter/timer specs:
power supply: 12-24VDC
Operational Voltage: 90-110%
power consumption: about 4VA
Max counting speed 2k cps
min signal width: min 20ms
Input: Impedance by shot

Circuiting contacs: Max 1KΩ
Residual voltage: Max 0.5V
IMpedance by opening: Mon 100kΩ
Input Impedance: 20kΩ

I am not sure if I explained this or not but the 6.2V I had in my schematic was just the measured amount I got from my Voltmeter.

It looks like you added some additional capacitance between the Vcc and ground on the chip? Then upped the capacitance between pins 6 and ground? Will this stabalize the wave form?

 

Oh, and it is a TLC555 CMOS. Thanks again for taking the time to look at this!