Thanks for the replies on the drawing question, Larry I love your emoji things, still chuckling :)...
Ok, so I thought the rectifier diodes allow current to flow in one direction only, thus allowing the current to flow through the pump from positive to negative, but not the other way around...? And I thought capacitors were there to prevent spikes and fluctuations in the current, which to my untrained brain, seems to reasonably do that in the figure 2 diagram...
I was wondering if Figure 1 was just drawn the way it was because that's an efficient use of space on a page, but it sounds like having those "jumper" wires before and after the pump with the capacitor and diode are actually how it's physically supposed to be wired.
I guess what I don't understand is why is figure 1 effective? can current not bypass the diode and the C2 capacitor and just flow through the C1 capacitor and pump whether the switch is open or closed? Wouldn't this always be the path of least resistance? See attached image for reference if needed...
Ahhh... I see... I didn't realize the capacitors were blockers, I thought they were just "mitigaters" for lack of a better word... if I had switched the direction of the diode, would that have eliminated the reverse bias and made the pump work? aside from the capacitors that is...
If the 120V AC receptacle that supplies power to the 5V DC wall adapter (which would be the supply for the relay module), also supplies power for the 120V AC devices that the module is controlling... AND supplies the 9V DC adapter for the Arduino... is this electrically separate? or are you saying that I would need to supply the 5V DC adapter for the relay module from a completely different 120V AC circuit?
They all can be powered from the same 120V AC circuit. Both the 5V adapter and the 9V adapter will have their outputs isolated from 120V AC. They will also be isolated from each other. Follow the connection scheme provided and it remains electrically separate.
Would a 5V adapter such as this be a good choice? does the built in noise filter have any benefit in this application?
Its a good choice, anything rated 1A or higher is OK. The noise filter wouldn't have much benefit here because the relay control circuit can tolerate noise. Also noise can't travel through the opto-isolator back to the Arduino.
When you say increasing the distance between components may help, are we talking a scale in feet or inches or yards?
The isolation should resolve any problems ... however if not, then arc suppression like an MOV or RC snubber or Ferrite core would help. If not resolved at this point, then it would help to increase the distance to 1-3 ft (or more if possible) from the Arduino board to the relay and AC circuit.
Hi dlloyd, thanks for the info! been doing some research into arc suppression and it sounds like a pretty good idea to extend the life of your relays or mechanical switches even if it isn't causing disruptions with your circuit and other hardware... this site seems to have a nifty little unit, no pricing or online ordering though... that always makes me think $$$$... ever heard of it? NoSpark
They also seem to suggest that snubbers aren't really all that effective... but maybe that's just because they're trying to sell a competing product?
On a totally unrelated topic, if you happen to have any thoughts on this, I'd love to hear them... I figure I should probably be looking to pick up a soldering iron at some point and was just wondering if all soldering irons are more or less the same or if that is one of those things that you get what you pay for...?
Also totally unrelated, I'm going to need to attach a spool to the shaft of my little dc motor and I was curious if you had any tips on the most effective way to do that? I'm guessing guys with machine shops or drill presses (I have neither) just make their own adapters, but I thought I'd ask just in case there's some tips out there
Hi dlloyd, thanks for the info! been doing some research into arc suppression and it sounds like a pretty good idea to extend the life of your relays or mechanical switches even if it isn't causing disruptions with your circuit and other hardware... this site seems to have a nifty little unit, no pricing or online ordering though... that always makes me think $$$$... ever heard of it? NoSpark
Yes, however their modules are quite costly and need to be sized to the load. It would actually be cheaper to go with zero-cross switching SSRs for your AC loads which are optically isolated, have no EMI and are easy to connect.
What stage are you at ... did you configure your connections to use relay board's opto-isolation?
Have you done any tests?
What specifically are the 3 120VAC devices?
Note there are lots of lower cost solutions that will do a good job reducing contact arcing and resulting interference problems. MOV's, Ferrite Beads, RC Snubbers.
Right now I'm just planning... still waiting for some components to come in, but most should arrive tomorrow so I'm hopeful I'll be able to start putting some things together this weekend and see if I can get things roughly working as they should.
the 3 120V AC devices will include a light bulb (possibly 2), a small 15W aquarium water heater, and the third will start out as a heat lamp (250W), but later I will convert it to a small fan(?W). If the lamp is too big of a load, I could probably run that separately as it will only be require for the first couple of months...
I plan to wire the relays up just like you suggested so they should be optically isolated.
thanks dlloyd... so I'd be looking at ferrite chokes to reduce interference and MOV for arc suppression...?
Normally, the ferrite chokes are used on the DC circuit power rails, however, in the link I provided they had success using them to reduce arc suppression by adding them to the AC load wire(s).
The MOV selected is good, I've had success using MOVs rated for 150VAC-175VAC on 120VAC circuits, but the 230VAC type you've selected is good. These are quite easy to install, they can just go across a relay's NO and COM terminals.
You may find no problems using just opto-isolation. But I would include the MOV's on the relays switching 120VAC as this would not only reduce EMI, but also help prolong relay contact life.
Using ferrite cores to reduce contact arcing is a less popular method, so you could reserve this for a last resort strategy. I haven't tried ferrites for this purpose as I've never had a problem using just opto-isolation and MOVs.
Its quite impressive how much preparation you've done ... I'm sure the project will be successful.
Thanks dlloyd, I didn't see a link in your last reply, but you referred to one;
in the link I provided they had success using them to reduce arc suppression by adding them to the AC load wire(s).
So were you suggesting the ferrite cores as an arc suppression solution or recommending them in addition to an MOV for reducing interference? If I install MOVs on the AC circuits, would i just then want ferrite cores for the DC circuit or would i use MOVs for all circuits? If I understand correctly they can be used for AC or DC circuits?
Also, that MOV I attached in the previous post... is it "over rated" at 230V for a 120V application? or is that more or less a maximum rating, which would be effective for 230V or less applications?
Its quite impressive how much preparation you've done ... I'm sure the project will be successful.
I do enjoy a good plan! The thrill is in the chase i guess... Also, this stuff is fascinating and I only wish I could learn more faster! I've got a few other project ideas kicking around in the back of my mind for when this one is complete and everything I learn now will make those ones easier
So were you suggesting the ferrite cores as an arc suppression solution or recommending them in addition to an MOV for reducing interference?
I was suggesting the ferrite cores for arc suppression. The MOVs are also for arc suppression and are probably all you need.
If I install MOVs on the AC circuits, would i just then want ferrite cores for the DC circuit or would i use MOVs for all circuits?
Use MOVs for the AC circuits only. Ferrites can be used on AC or DC circuits. With MOVs on the AC side, and opto-isolation on the DC side, you probably don't need the ferrites (but its good to have a few handy due to their all-purpose capabilities).
Also, that MOV I attached in the previous post... is it "over rated" at 230V for a 120V application? or is that more or less a maximum rating, which would be effective for 230V or less applications?
Its a little over rated for 120V applications but under rated for 230V applications (these should be rated at 275-300VAC). For 120VAC applications, I usually use 150VAC to 175VAC (don't go below 150VAC) ... here's a popular one at Digi-Key
Thanks everyone for all your help! I've started trying to put things together, but am having some trouble getting the LCD going. I've started a new thread at [SOLVED] I2C LCD - Setup instructions for 16x2 - Displays - Arduino Forum. If anyone has any thoughts, as always they would be very much appreciated!
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