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computer Christmas lights

MrDEB

Well-Known Member
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

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

What is "GRD"?
 

For The Popcorn

Active Member
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

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

For The Popcorn

Active Member
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.

SmartSelect_20220728-115123_Edge.jpg


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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.

SmartSelect_20220728-121535_Edge.jpg
 

MrDEB

Well-Known Member
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

Well-Known Member
here is a link to the LED strips I purchased.
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

Well-Known Member
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)
 

MrDEB

Well-Known Member
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

Active Member
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

Well-Known Member
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.
 

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