Electronics > Projects, Designs, and Technical Stuff
Can someone help me review this schematic?
moffy:
See if you can sketch out your idea on a piece of paper and then upload a photo. You only need to use rectangles for such things as the arduino. Don't worry about it being rough or incomplete, it is a starting point which can be built upon.
redgear:
Here is a simple block diagram of what I have in mind. Looking forward for your suggestions.
moffy:
Yes, that looks pretty good, and nicely drawn. You will need some sort of supply to drive the relay coil, you can use the 5v regulated, but 5v relay coils tend to draw a bit of corrent. What I tend to do is provide an unregulated 12v supply (what your transformer, bridge rectifier and caps provide). The transformer can have a 9v or 10v RMS secondary, when rectified and filtered will produce around 12v dc (with large enough caps). That can also be used to power your 5v regulator. Also 12v relays are plentiful because of cars. To drive the relay coils use a suitable transistor, and a flyback diode across the coil to reduce spikes.
redgear:
--- Quote from: moffy on July 07, 2020, 03:18:21 pm ---Yes, that looks pretty good, and nicely drawn. You will need some sort of supply to drive the relay coil, you can use the 5v regulated, but 5v relay coils tend to draw a bit of corrent. What I tend to do is provide an unregulated 12v supply (what your transformer, bridge rectifier and caps provide). The transformer can have a 9v or 10v RMS secondary, when rectified and filtered will produce around 12v dc (with large enough caps). That can also be used to power your 5v regulator. Also 12v relays are plentiful because of cars. To drive the relay coils use a suitable transistor, and a flyback diode across the coil to reduce spikes.
--- End quote ---
Thanks! I will make the changes and post a schematic.
mariush:
a small 5-15 VA 12v transformer + bridge rectifier + smoothing cap or a small 12v dc power supply.
A 7805 / LM317 / whatever linear regulator to produce 5v for the microcontroller and the LCD display.
ULN2003A (darlington transistor array) or something similar to turn the relays on and off (you can connect the microcontroller directly to this, instead of having resistor and npn transistor for each relay ... you have 7 transistor+resistor pairs inside a dip chip)
Some diodes for each relay (for voltage spike protection when relays turns off)
momentary buttons with resistor on each one to limit current, put all buttons on a port and maybe set interrupt on change ... when a button is pressed an interrupt is triggered and you have your value. (or just constantly poll the buttons which would be useful for debouncing purposes)
For extra fun, you may want to experiment with capacitive touch like you see on lots of devices .. see for example https://www.digikey.com/product-detail/en/microchip-technology/CAP1206-1-SL/CAP1206-1-SL-ND/5886099
whole category here: https://www.digikey.com/products/en/integrated-circuits-ics/interface-sensor-capacitive-touch/560/page/2?k=capacitive%20touch&quantity=50&stock=1&ColumnSort=1000011&pkeyword=capacitive%20touch
For example
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