The spring ground pin ruined several circuits

Nubility

The spring ground pin ruined several circuits [Copy link]

 

The spring ground pin used in the oscilloscope probe caused trouble again. A few days ago, I had to measure a switching waveform of a DCDC circuit. I couldn't use an alligator clip and had to use a spring pin for grounding. Because the capacitors and resistors used on the board are all 0402 or 0201, there is no GND test point nearby. Even if there is, it is a surface test point and cannot be fixed at all. Moreover, this time I was measuring two points at the same time. I didn't press it well for a while. The spring pin that was originally on the capacitor pin suddenly slipped and touched another component. The indicator lights on the board went out all at once. When I removed the two DCDCs and measured them, it turned out that they were both short-circuited internally. After thinking about it, I also tried to solder the spring pin directly to the component pin or test point, but the spring pin just wouldn't eat tin. The most effective way I can think of now is to change all the test points to through holes opened on the surface, and the hole diameter should be large so that the spring pin can be directly stuck. This is safe.

lugl4313820

You can use a wire to lead it out, otherwise if there is a short circuit, everything will be destroyed!

qwqwqw2088

The spring pin is not easy to solder, so it needs to be scraped.

Solder a very short component leg, bend it and hook it

Nubility

lugl4313820 posted on 2023-8-20 13:43 You can use a binding wire to lead it out, otherwise if there is a short circuit, everything will be gone!

No, the purpose of using a spring ground pin is to reduce the ground loop. Using a Dupont wire is no different from using an alligator clip.

Nubility

qwqwqw2088 posted on 2023-8-20 16:06 The spring pin is not easy to solder. It needs to be scraped and soldered. A very short component leg is bent and then hooked

It still can't be welded after scraping. Maybe stainless steel itself is difficult to weld?

led2015

There is a reason why slow work produces fine work. Try using a passive probe, which can reduce interference with the circuit.

Nubility

led2015 published on 2023-8-20 19:17 There is a reason why slow work produces fine work. Try using a passive probe, which can reduce interference with the circuit.

What is a passive probe: time:

吾妻思萌

Testpad. All leads are connected and labeled.

Nubility

Azuma Simeng posted on 2023-8-21 07:34 testpad. All wires are drawn out and then labeled

No, first of all, I am afraid that the soldering wire may be pulled off by the onlookers accidentally. My board was originally very good and I don’t know who broke it. Secondly, the soldering wire will increase the loop of the probe and make the signal quality worse.

wangerxian

When designing a circuit in the future, design a test point in advance. This time, ask someone to help you with the test and discuss knowledge with him.

Nubility

wangerxian posted on 2023-8-21 09:29 When designing a circuit in the future, design a test point in advance. Ask someone to help you with this test, and discuss knowledge with him by the way.

The test point must be set as a large through hole. The test point of the surface pad is not suitable for using an ordinary oscilloscope probe.

laker2008

Next time, you can try to put the spring needle to the grounded end of the nearest capacitor, and then use the probe to find the signal pin. Try it several times. It is not easy to measure the signal with this thing. Sometimes it takes two people to measure it.

wangerxian

Nubility posted on 2023-8-21 09:56 The test point must be set as a large through hole. The test point of the surface pad is not suitable for using an ordinary oscilloscope probe

Yes, vias are more reliable.

lkh747566933

Find a thin wire to tie the spring pin and the probe together to limit its range of movement, or put some tin on the GND pad to make a pit to facilitate the fixing of the spring pin.

lkh747566933

Nubility posted on 2023-8-20 17:08 No, the purpose of using a spring grounding pin is to reduce the ground wire loop. Using a Dupont wire is no different from an alligator clip

Is the effect of testing with DuPont wire worse than the original ground wire of the probe?

吾妻思萌

Azuma Simeng published on 2023-8-21 07:34 testpad. All leads come out and are labeled

No, first of all, I am afraid that the soldering wire may come out and the pad may be pulled off by the onlookers accidentally. My board was originally very good and I don’t know who pulled it and broke it. Then the soldering wire will increase the loop of the probe and make the signal quality worse

It cannot be soldered on the pad. When laying out the pcb, you need to reserve testpad vias to solder waste pins, or else use pin headers.

吾妻思萌

The solder pad is broken and even the gods can't save it. I really want to fix that little bit.