Mosfet Circuit

[ILikeComputers]

I just finished this schematic. I just wanted someone to review it before I bought the parts.

The first file is the schematic as a png. The second file is the EAGLE schematic in a zip folder.

Thanks so much
-ILikeComputers

 

[Grossel]

I found a problem with the circuit. R1 has an disconnected pin (should most probably be connected to ground). Thats makes emitter voltage at T2 being around 4 volts all the time, and a little change in PH1 will have virtually no effect.

 

[audioguru]

Since the schematic is zipped instead of posted as a quickly opened PNG file type, then I won't look at it.

 

[ILikeComputers]

Thanks Grossel. Tell me if that is what you meant.

Audioguru,I have added the png separately from the zip file.

Thanks
-ILikeComputers

 

[Grossel]

Thanks Grossel. Tell me if that is what you meant.

Yes, exactly

 

[audioguru]

The Mosfet is shown connected completely wrong, the 5V regulator is missing the important input and output capacitors and the LEDs do not have current-limiting resistors.

 

[ILikeComputers]

AudioGuru could you please explain more. I would like the help.

Thanks so much
-ILikeComputers

 

[Mikebits]

You have the load pin hooked up on the counter for some reason but, your ABCD pins are left unconnected or floating so no telling what your going to load. Perhaps you should explain what the circuit is supposed to do.

 

[audioguru]

AudioGuru could you please explain more.

You show a big long part number for the Mosfet but it does not make sense so datasheetarchive.com could not find its datasheet.
It is drawn as an N-channel Mosfet.
Its gate is usually its input but yours is connected to a motor.
Its source is usually grounded but you show it as the input.
Its drain usually connects to a positive supply voltage but yours connects to ground.

Look at the datasheet for the 7805 regulator to see the important input and output capacitors.

LEDs and laser diodes are diodes. If you do not limit the current then they blow up. Your circuit does not limit their current.

 

[ILikeComputers]

Thanks Audioguru. The laser already has a resistor. It is going to be mounted "off board". Wouldn't R1 work to limit the current for my led? I also fixed the Mosfet ( or at least I think I did).

Mikebits, thanks for pointing that out. I had accidentally connected it to load instead of clear. The circuit is supposed to count the number of times to beam of light between the counter led and the photo cell. When it reaches 3 the motor is supposed to turn off. When the trigger switch is released the counter is supposed to reset to 0.

Datasheet for Mosfet: https://www.electro-tech-online.com/custompdfs/2010/07/NSQA6V8AW5T2-DPDF.pdf
and the part: ON SEMICONDUCTOR|NTD20N03L27G|N CHANNEL MOSFET, 30V, 20A, D | Newark.com

One more question. The circle on the input pins on the chip, do they mean that the single is inverted?

The schematics have been updated.

Thanks
-ILikeComputers

 

[Mikebits]

one more point. All unused pins on the cmos counter should be tied to an appropriate logic level and not left floating.

 

[ILikeComputers]

Should I just connect them to ground? And how about my NAND chip. Should I connect the unused pins to ground?

Thanks
-ILikeComputers

 

[Mikebits]

Load pin should be pulled high. For ABCD pins ground is fine. For the gates I did not see any unused pins. Why are you using obsolete parts for your gates?

 

[ILikeComputers]

There. The schematic is updated. I am not sure what you mean by my gates are obsolete. I found a datasheet and the part.

One other question, do the circles on the chip mean the signal is inverted?

Thanks soooo much
-ILikeComputers

 

[Mikebits]

Yes, the bubbles indicate that a signal is active low. Also it would help if you spread out the schematic, it is somewhat crowded and hard to read. Just trying to help.

 

[ILikeComputers]

Thanks.
Do you really think that i need filtering capacitors for my voltage regulator? I tried once. I am using a 12v lead acid battery for my supply. The capacitor exploded.

 

[audioguru]

Ceramic disc or ceramic multi-layer capacitors are usually used for voltage regulators. Tantalum capacitors explode. Electrolytic capacitors also explode if they are connected with backwards polarity.

 

[ILikeComputers]

oh thanks

Does the mosfet look wired correctly?

Thanks
-ILikeComputers

 

[audioguru]

Now the Mosfet is drawn correctly. But its gate and the CLEAR input of the counter "float" without a logic level when the push-button is not pressed. It needs a pullup or pull-down resistor.

 

[ILikeComputers]

I am not sure what you mean. Could you please give me an example.

Thanks
-ILikeComputers