computer Christmas lights

[MrDEB]

years ago I assembled a Compurterized Christmas light display but since sold the entire setup.
I recall the SSR or triac boards used an opti-isolator, couple resistors but instead of using a computer, I want to just use a PIC to drive the opti_isolator. Just started looking for leftover plans and parts but figure would ask first.

 

[For The Popcorn]

Are you waiting for somebody to connect the dots for you?

What is "GRD"?

 

[For The Popcorn]

Before anybody says it's obvious that "GRD" is ground, no it is not. The ground connection at the voltage regulator is called GND. The ground symbol is GND. GRD and GND are not the same net and won't be connected. Errors like this are how you end up with scrap boards. In coding, circuit board layout and life, spelling counts.

Feeding the 7805 12 volts shouldn't be an issue. The only 5 volt load is the micro.

 

[For The Popcorn]

Ummm. I think you want N channel MOSFETs, not the P channel shown – P channel will require complications to make work with no payoff.

 

[tumbleweed]

yeah, and don't pull up the pic output pins with 12V either.

If you change it to N-chan then switch "GRD", not 12V side.

 

[For The Popcorn]

To illustrate the difference between using P-channel and N-channel MOSFETs.

The most common MOSFET switch uses an N channel MOSFET as a low side switch. The load is connected between its positive voltage source (which may be as high as the MOSFET rating) and the MOSFET. When the MOSFET is 'on', the load is connected to ground.

------‐------------------------------------------------------------

Alternatively, a P channel MOSFET may be used as a high side switch. The MOSFET switches the positive voltage source to the load, which is connected direcently to ground. The complication is that to turn the MOSFET off, the gate must be connected to the source voltage – the positive voltage supply. To allow a microcontroller to control a high side switch, an additional transistor must be added to the circuit.

 

[MrDEB]

looking at my BOM from Mouser in 2017 I see the parts I purchased for several boards I built for a band competion.
I need to locate the one board I have that has IRLZ44NPbF mosfets and the bom shows transistors as well.
Need to decide to build a completely new board with SMD components or use what I have.
The LED neon strips need 60 watts at 12 volts=5 amps.
decisions, decisions.

 

[MrDEB]

here is a link to the LED strips I purchased.

Led Neon Rope Light 12V Flexible Led Strip Lights IP65 Waterproof 1-5M 8 Colors | eBay

Waterproof: IP65. The LED neon lights, uniform illumination, suitable for advertising signs, letter signs, display signs, contours, table / table / bed / car / wall decoration, suitable for indoor / outdoor / year-round use.

www.ebay.com

best I can figure is 1 amp per meter of LED rope.
1 meter = 39 inches.
Way over kill on the mosfets. Maxium for entire sign is less than 5 amps
rethinking mosfet size. each mosfet only needs to carry 1 amp or less.
The logic level n channel as post #25

 

[MrDEB]

after researching numerous mosfets and viewing youtube videos I found a mosfet that should work (same mosfet as the Ardunio mosfet board) https://dronebotworkshop.com/transistors-mosfets/
here is a revised schematic for 1 of 12 channels

 

[Pommie]

The 12V in seems to only have the positive connected.

Mike.

 

[MrDEB]

Plan to put the 12v ground in one of the planned headers. Waiting for parts before determining the final connection. I ordered the 10-position wire to board headers from Jamco Electronics as well as the IRF520. The MOSFETs were 77 cents each. After printing out a board, then check if the components fit then order boards.
Been contemplating maybe some led dimming (pwm)

 

[tumbleweed]

Plan to put the 12v ground in one of the planned headers.

You mean like putting it in the power supply connector J2?

 

[MrDEB]

something like that, but waiting for the 12v power supply to determine what I need in pcboard.
Looking over the data sheet for the 18f2221 I see no pwm port pins so dimming is kinda out unless I use same routine I used in the Christmas Star project.
Nothing is in stone yet, still looking at options etc.

 

[tumbleweed]

The 18F2221 has 2 PWM channels, but I think you've been doing all your "pwm" using software.

Probably better that way... stick with what you've been doing. Besides, it's not like the pic has a lot of anything else to do.

 

[MrDEB]

That's the plan. Need to figure out how big (cost) for the board but contemplating on perfboard but the 18f2221's I have are SMD unless there is a "breakout board" that can be soldered onto a perf board?
doing some searching. The only connections are the voltage reg.and 12 mosfets plus the ICSP port.

 

[MrDEB]

I think I finally got this board configured. I added more mosfets just in case I need a different led/neon sign needing more led strips. This project I only need to use 8 mosfets and 3 "flaming candle"leds.

 

[MrDEB]

second page

 

[MrDEB]

got the board designed but hoping for some input on my schematic.

 

[tumbleweed]

You might want to reduce value of the series resistor on the mosfet gates.
The higher that value, the slower the fet will switch (due to the gate capacitance).

 

[For The Popcorn]

Your unique schematic style of having all the components as stand-alone pieces with the connections indicated only by labels instead of lines makes it rather tedious to follow. In order to know what may be connected to a given point, EVERY label must be scanned to be sure what's connected where.

You may know only one thing is connected to port B1, but nobody else does until every label is examined.

It's ok to break out functional blocks this way, like the power supply for example, but even within that section, you've used the same (adjective deleted) technique. Instead of showing the voltage regulator's caps as connected between the voltage regulator input/output pins and ground, you used labels to show the input cap connected to +12v and the voltage regulator's input connected to +12v where just drawing a line showing the connection would have been so much clearer. You've managed to take what should be a picture and convert it the 1000 words.


Putting all of the above aside, the only shortcoming I notice is that you don't have return connections (don't know if power or ground) for your flame LEDs. Your connection blocks for the other LEDs are probably OK, but your intentions aren't completely clear.

 

[MrDEB]

I used to show ALL the connection wires but was mentioned it is too hard to figure out what was connected to ?. using ESAYEDA schematic as an example to draw a schematic.
Will lower the gate resistance to the mosfets.