Introduction

Hello, I'm Dophie.
About half a year has passed since I joined the company.
So, in this article, I would like to introduce you to a rookie mistake I made in the six months after joining the company.

Failure 1 ~Current does not flow...~

A Conversation One Day in May.

Me: “Senpai, current doesn’t flow through resistors.

Senpai: “No, no, show me the circuit diagram.”

Here is a simplified version of the actual circuit diagram (Fig. 1).

Senpai: “In this circuit, current should flow. Why can’t it flow?”

With that said, my senior was very surprised when he saw the actual wiring (Fig. 2).

Senior: “Why is this part not connected to anything? (Figures 1 and 2, red circle) If it is open, no current will flow.”

It was a very embarrassing failure for us.

Failure 2 ~I can't get the parts...~

Conversation one day in July.

Me: "Senior, I broke a component (power supply IC and inductor) again..."

Senpai: “Why are you so broken? LOL”

Me: "When I removed the parts, the legs of the parts were burned out..."

*Parts were removed when changing the parameters of the part (inductor value or resistance value) or when it interfered with the replacement of other parts.

Senior: “Isn’t that a bad soldering method? How do you remove the parts?”

I said, "I'm just trying to remove it by applying a soldering iron!!!" (Fig. 3)

upperclassman"·······.
Soldering is more difficult when unsoldering than when soldering.
When removing, first pour a large amount of solder onto the land. Then the heat spreads all over the part and it comes off easily. ”

I said, "What?! I'll try!!!"

-Trying to remove parts using the method taught by seniors-

I said, "It was easy to remove!!!"

Fig. 4 shows the process (the correct way) until the part can be obtained.

Around July, it took me just under an hour to remove one part.
I've gotten pretty good at it now and can remove parts in less than 5 minutes on average.

Mistake 3 ~Be careful before the experiment~

An event in August.
After wiring the circuit, I turned on the switch of the regulated DC power supply (a device that supplies voltage) to conduct an experiment.
Then, for a moment, a small amount of smoke danced in the air.

Naturally, I will be "Eh...!?!?"

The cause was in the DC stabilized power supply.
A stabilized power supply has a power ON/OFF switch for the device itself and an ON/OFF switch for voltage application.
First, turn on the power of the device itself, then set the voltage to be applied and press the OUTPUT button to apply the voltage (Fig. 5).

However, in this case, the OUTPUT button was already ON when the device itself was turned on.
The set voltage is 12 V. The absolute maximum rating (input voltage) of the demo board I was using at that time was 6V.

Of course, 12 V was applied to the demo board the moment the device was powered on, so it's not surprising that there was smoke.

Through this failure, I learned that it is necessary to check not only the wiring but also the state of the equipment (such as how the previous user turned off the power) before the experiment.

In addition, the regulated DC power supply in Fig. 5 allows the user to set the current limit value, and the limiter can be applied at the set value.
Therefore, I also learned that this failure could have been prevented if I had set the current limit.

at the end

Now, let me tell you about a mistake I made.
Looking back, it's all really rudimentary and embarrassing.

In the future, I would like to be devoted to these failures.
Failure collection part 2 will be delivered again in 2-3 months.

Thank you for your next article!

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