MCLR resistor

[The Master]

Im 99.9% sure that the code is right. Ive checked it and tested it and its all fine. Im pretty sure its noise. I had a solenoid connected to it through a relay which made it reset everytime the solenoid fired. i put a diode accross the solenoid and that worked. Ive also got it connected to a smoke machine using a relay. I tried using the normal button (circuit not connected) but still it reset itself at the other end of the room. Im testing out a triac on the smoke machine and things seem to be improving.

1 last problem i have is to connect the strobe up to it. I modded my stobe a few years ago so a remote controller could be plugged in. just a simple push to make switch at the end of the wire. For this year i replaced the switch with a relay and again this caused problems. Unfortunately a triac doesnt work on this circuit. Is it safe to connect the mains side of the strobe to a triac?

[The Master]

Oh yeah. If i turn the mains off to the strobe/smoke machine and the 12V to the solenoid then the whole circuit works perfect and all the relays operate properly. Its only affected when there is a load on the switching side of the relays. The solenoid one is next to the chip so i can understand but the other 2 are on the end of a long wire next to the strobe/smoke machine

[Melanie]

> Is it safe to connect the mains side of the strobe to a triac?

Most Triacs seem to have mains connected to them... but it all depends on your circuit...

[The Master]

Its a strobe though. IVe been warned not to connect inductive loads like transformers. Do strobes count?

[Melanie]

If you use a Triac as a switching device - ie purely as an ON/OFF switch then you can happilly switch inductive loads if you follow all the design rules and read your Triacs Datasheet to ensure suitability.

There's nothing wrong with Relays either as long as you drive them correctly. In the attached picture (which is a popular industrial controller), the 18F PIC at the upper right, switches 12v Relays (black cubes) via a ULN2004, which in turn switch 240vAC contactors, which in turn switch 15kW 415vAC 3-Phase motors - all in one neat package with no noise issues concerning the PIC. That PIC is only 100mm away from noisy and spikey 415v (the Transformer in centre). The board is run from 12vAC, rectified and smoothed with two 470uF Capacitors. This raw unregulated supply drives the Relays, and THREE (yes three) 78L05 Regulators, one of which is dedicated to the PIC and it's support IC's. There's only 10uF sitting on that +5v Supply Rail, but a further 10 x 100nF's dotted around the board.

[The Master]

Very strange then. Im only switching 240V max. The smoke machine has the highest rating at 750W but most of that is for the big heating coil and so the relay shouldnt have much to deal with at all. Using a triac for the smoke machine is definately helping. Its hardly reseting itself at all now. The solenoid seems to be working fine and in about 500 operations has only caused a reset once. Im going to replace the 10K resistors with a plain wire and see how things go then. A teacher at my old school said 10K might be too much and MCLR isnt getting enough power.

The real test will come in a few hours when i try running 3 smoke machines, 1 strobe, 1 solenoid and about 20 LEDs from it at the same time.

BTW, when you say "purely on/off", what else could it do?

[Melanie]

Oh... and in the board above, MCLR is strapped directly to Vdd. There's more to it than first meets the eye... careful positioning of components, ground-plane around the PIC and little ditties like that all come together to produce a solid bullet-proof final product.

> BTW, when you say "purely on/off", what else could it do?

By varing the firing angle you use Triacs to dim lighting for example. It's actually VERY EASY to switch Triacs badly, and so create heaps of noise and inductive nightmares (kinda apt for halloween).

[The Master]

I dont understand that. Do you mean like PWM? That is still on/off. The person who gave me that diagram also made me some boxes. Each one accepts serial input and uses PWM to fade the outputs. Im already using these for some of the lights but when he made them he warned me not to connect any transformers or even UV lights. Im wondering if connecting a strobe would damage them. If not then i dont have to have to strobe on my circuit at all.

What is the worst that could happen? The internal chip is protected by optoisolators and each output is fused. I accidentally blew a triac once (under normal use) and it was hard to replace. All 8 triacs are rivveted to the side.

What do you mean by ground plane? Is that just a lot of grounded copper on the PCB? This circuit is running from a breadboard. I will make something more profesional next year when i have time and equipment.