Forum Replies Created
-
AuthorPosts
-
April 15, 2019 at 4:51 pm in reply to: Question about schematic used in quiz question 4 and 5, unit 5 part 2 #15704
A check from one of the output terminals to one of the input terminals would not be useful here. As part of the setup for this question, you already have as a given that your power supply up to the noise filter is good. So you know the component has a good input. The only test you need to make is from L2 wrt N2, since those are your two output terminals. That will tell you if the noise filter is capable of putting out a good 120 VAC.
The question is supposed to throw you off your game, so don’t worry — it’s just doing it’s job! 🙂
The point of it is to teach you to always pay attention to text in schematics. If the engineers took the time to write a special note for you, you can bet it’s something important. In this case, they tell you exactly which two wires provide the input, and which two provide the output.
Since they’ve given you this info, you don’t need to know anything about the inner workings of the noise filter. You can just treat it like a black box. Check that it’s getting a good 120 VAC power supply. Then check that it’s putting out a good 120 VAC power supply. That’s it.
I believe that the concept of inputs and outputs is covered in Fundamentals, and it’s definitely covered in detail in the Advanced Troubleshooting course’s material on control boards.
The concept isn’t too complicated. An input is just whatever is supposed to be supplied to a particular component, and an output is just what it’s supposed to do in response to the input.
As a very basic example, let’s think of a motor. The input is just the power supply: 120 VAC on one side and neutral on the other. In response to being supplied with power, the motor outputs mechanical motion. Another example is that noise filter we’ve been talking about elsewhere in the forum. Its input is the power supply coming from the wall outlet, and its output should simply be that same power supply.
We talk about inputs and outputs the most when we’re talking about control boards. This is because boards are programmed with logic that’s supposed to produce certain outputs in response to certain inputs.
Whether a particular component that’s connected to the board is supposed to send the board an input or receive an output from the board is rarely called out explicitly — but it’s not hard to figure out by common sense. Just think about what a particular component’s intended function is.
For example, a control board in a refrigerator will receive input from thermistors telling it the temps in various places around the refrigerator. If the board receives an input telling it that the freezer compartment is too warm, then it will probably send power (an output) to the compressor. The thermistor sends input to the board, and the compressor receives output from the board.
We’re not always privy to exactly how a control board is programmed to make decisions — that’s a place where we’re at the mercy of the manufacturer to provide that info. But identifying what’s supposed to be an input and what’s supposed to be an output is relatively simple.
And a Wiggy is just a brand of loading meter. Amazon is probably the best place to get one.
They are both physically located on the motor, but they are in fact two distinct switches with different purposes.
The centrifugal switch in the motor’s circuit is there to take the start winding out of the circuit once the motor has begun to spin. This is pretty standard stuff for split-phase motors.
The other centrifugal switch in the L2 side of the heater circuit is there as a safety. The engineers put that there to keep the heater from running if the motor fails to start. If the motor doesn’t start spinning, the heater circuit will never close.
April 11, 2019 at 9:09 pm in reply to: Question about schematic used in quiz question 4 and 5, unit 5 part 2 #15694You’re correct that you should make your test at L2 wrt N2, but it’s not to check for voltage spikes — you probably won’t be able to detect the kind of noise that this device is supposed to filter out. All you need to do is make sure that, if you have a good 120 VAC power supply going into the filter, you get a good 120 VAC coming out.
Hi Jason,
Let’s go through your questions one at a time.
1. “Cam” is just the term used to refer to the physical switch inside of the timer.
2. For a switch to be “made” is just a common phrase that means for the switch to close — exactly as you thought.
3 (and 4). Probably why that diagram is throwing you is because you’re trying to look at it as a transformer, when it’s actually a noise filter. I saw your response to another topic in this forum which seemed to indicate that you had mostly figured this out, but just for clarity…
You don’t need to worry about any of the funky stuff (coils, capacitors, etc.) that you see in the diagram. All you’re concerned about is that, if you’re getting a good 120 VAC power supply in, you’re also getting a good 120 VAC power supply out. There’s even text in the diagram telling you which side is the input and which is the output.
The L1/L2 nomenclature in this case is not referring to a 240 VAC configuration. In this particular diagram, the manufacturer (for whatever reason) decided to mark the inputs to the noise filter as L1 and N1 and the outputs as L2 and N2. A little confusing, but again, there’s text right on the diagram saying what’s the input and what’s the output.
Make sense?
The schematic will always be the best way to determine this, hands down. There’s no easier way to determine whether it has an inverter.
April 4, 2019 at 3:49 pm in reply to: Advanced Schematic Analysis and Troubleshooting-A two speed motor. #15656Assuming we’re looking at the same part of the video (about 14 minutes in), then yes, there would definitely be line present on both sides of the regular speed motor winding.
That’s because, in this scenario, that 32 to 16 switch in timer cam 6 is stuck open. If that’s open, is there going to be any voltage drop across the motor winding?
When someone says that something is failing under load, that’s a very general statement. There are a lot of different possibilities.
In the specific example of a pump motor, you could have a mechanical problem that causes it to fail under load. The motor could test perfectly fine electrically, but when you apply power, it’s physically incapable of turning — for example, if it’s jammed.
Another case for a motor would be if its windings are contacting ground — the windings might check good on ohms, but when you try to run the motor, you’ll have current flowing to ground instead of neutral. You would, of course, be able to check for this one by measuring continuity from the windings to ground, but people don’t always think to do this.
And those are just two examples. There’s not a silver bullet for identifying if something is failing under load, except by simply identifying that there is a proper power supply right up to the load, and yet it’s still not doing what it’s supposed to do.
If you’re only reading 80V of voltage drop across a load that’s supposed to drop the full 120V, you’re most likely dealing with a high-resistance connection in that load’s circuit, not a problem with the load itself.
When you have only a single load in a circuit, it will always drop all the voltage. But if you have two or more loads in series (even if one of those “loads” is actually just a high-resistance connection), then the voltage drop will divide between the loads according to their resistance.
Make sense?
When it comes to testing a hall sensor, you’re very much at the mercy of whether the manufacturer provided specifications and pinouts. There are different ways that hall sensors can be implemented, so you need to know what specific voltages/resistances you should expect, and where.
For an example of a particular hall sensor configuration, see this page: https://appliantology.org/gallery/image/733-wiring-harness-and-resistance-checks-on-the-hall-sensor-in-an-lg-washer/
As for phase rotation meters, you can find plenty on Amazon. Here’s the one we have: https://www.amazon.com/Sequence-Presence-Rotation-Indicator-Detector/dp/B018Q2CMPY/ref=sr_1_7?ie=UTF8&qid=1550438244&sr=8-7&keywords=phase+rotation+meter
February 11, 2019 at 7:50 pm in reply to: In regards to circuits breakers panels and power outlets #15374The fact that you can safely touch a neutral wire is stated in the first video of module 3 unit 6.
Additionally, with everything you learn throughout units 1 – 8 about the nature of voltage, voltage drop, and the neutral wire itself, you can figure out that neutral would be safe to touch, even before it’s explicitly stated in the text of unit 9.
There you go! Looks like you’ve figured everything out. Anything still not clear?
Looks to me like it’s not hardwired — there’s something between the indicator light and L1. What is that?
Correct! So that’s one way that L1 gets to the hot indicator light. The other way is a lot easier to see. Do you know what it is?
-
AuthorPosts
