Safe Circuit Board Power-Up: Troubleshoot like a Pro
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- Опубликовано: 5 авг 2024
- Are you looking for a way to power up your new PCB design safely? In this article, Mark shares his expert strategies to minimize the risk of damage to the board or components during the first power-up. Don't let your hard work go to waste - read the article to learn more about using a multimeter, a current-limited power supply, and a thermal imager to identify problems with your board and bring it online for the first time safely.
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Two additional items to consider:
1. Use 0R to disconnect the load from your regulator outputs when first powering up. This will protect your circuit if there is an issue you didn't pick up. You can then also test to ensure the output voltage in a no-load condition
2. With the abovementioned 0R removed, you can temporarily add load resistors to confirm your power supply current capability
3. Add the 0R links back. Any errors now will be on the load side, not the power supply side.
Recommend adding the following steps:
Measuring resistance of all rails with both polarities of multimeter (positive biased lead on rail to negative biased lead on ground and vice versa). PN junctions present in sneak paths, such as protection diodes in CMOS devices, may yield different leakage currents depending on bias polarity of the resistance measurement. Record these measurements and trend across serial numbers. Out of family results may indicate a defect.
If using sensitive low voltage devices, such as modern FPGAs operating at ~1V core, check the open circuit test voltage of your multimeter in resistance mode with another meter in voltage mode for damaging test voltage levels. For example, many Fluke meters have open circuit test voltages upwards of 5V. This can damage a 1V rated device if applied directly to the core rail. For this reason, I like to use an Amprobe 37XR-A with an open circuit test voltage clamped to around 250 mV.
Prior to applying power to the board, independently verify the supply is configured properly by measuring the open circuit voltage of the supply with a volt meter, and then verifying the over current trip threshold by shorting the leads together. Make sure you understand the type of over current protection being provided - foldback current protection behaves very differently from a strict cut off protection, for instance.
Also, be mindful of your lab supply's voltage slew rates. A rise time that is too fast may result in inductive kicks through the cabling to the DUT. A rise time that is too slow may result in startup issues at the DUT. In general I've found a primary supply rise time of 1-10 ms to be sufficient for just about everything I've ever touched.
These are some good points. Speaking to the modern FPGA devices.. I’ve found that measuring the resistance across the main core rails often results in resistance well under 50 ohms from power to ground. This is a consistent result across serial numbers as well, so as the video suggests, at the end of the day know or have a rough idea what to expect based on design.
@@CSFitness1 Can confirm. I'm currently working on a design featuring a Xilinx Ultrascale device. I've consistently measured a core rail impedance of about 20 ohms using the aforementioned Amprobe 37XR-A meter. The leakage currents are surprisingly large.
Your emphasis on understanding the schematic while measuring resistance is essential. It's all about knowing what to expect and spotting deviations.
To prevent accidental shorts, you can cover the board with an insulating material like Kapton tape, leaving only the areas you need to probe exposed.
Mark, your videos are absolutely fabulous and the best Altium has ever put out.
Double-checking part numbers and pinouts is something I've learned the hard way. Thanks for highlighting this common issue.
It's great to see a focus on the use of proper tools and equipment in this video. Quality tools can make a world of difference when working with circuit boards.
I've been working with circuit boards for years, and I can't stress enough the importance of using a current-limited lab power supply. Great advice!
I've seen many engineers overlook the importance of inrush current management. Thanks for emphasizing this crucial consideration.
Your method for checking the output voltages of regulators is exactly how I approach it. It's a critical step in verifying a board's functionality.
I've used a similar approach to powering up new circuit boards throughout my career. Consistency is key in avoiding potential issues.
Thanks for the clear explanations, Mark! I'm always learning something new from your videos.
Excellent walkthrough, Mark! Your videos always make complex topics much more approachable.
Great video, Mark! I've always been nervous about powering up a new circuit board. Your step-by-step guide really helps.
I've just started learning about circuit boards, and this video is very informative. Thanks for sharing!
A good practice is to use an oscilloscope to check for any unexpected oscillations or noise on the power rails.
One tip I've found helpful when troubleshooting is to keep a notebook of past issues and their solutions. It can save time when encountering similar problems in the future.
I wish I had seen this video before I accidentally fried my last project. Lesson learned!
Looks like a cleverly arranged lab setup. Would love to see some practival lab tools & setup tips video.
A tip I've found useful is to have a copy of the schematic and layout nearby when troubleshooting a new circuit board. It can help with quickly identifying potential issues.
Thank you for sharing debugging process, can you please share the link to the thermal camera.
Don't forget re power rail resistance measurements that capacitors can look like a low resistance so give the multi meter time to make a better measurement
Great video! Can you recommend any resources for learning more about PCB design and troubleshooting?
Great video! Btw,Where do you get the aluminum rack that holds all your test equipment on the right of your bench? I love the setup.
Thermal imaging cameras are such a game changer! Which model do you use, and would you recommend it for beginners?
Some circuits will not boot properly unless given its operating voltage at start-up. My ZVS was running on 4V 3A, maxing out my power supply. However all resistance measurements check out and I was in a hurry. So I thought why not give it a shot. So I disconnected, turned up to 15V and reconnected, this time it only took 0.3Amps and was switching as expected. When it falls below a threshold voltage, it stops switching and turns into a short.
I've never used a current limited lab power supply before, but it sounds essential. Any recommendations for a beginner-friendly one?
I'm curious - have you ever tried using a multimeter with a temperature probe for troubleshooting instead of a thermal imaging camera?
In my experience, paying close attention to the quality of solder joints can save a lot of headaches during the initial power-up process.
How did you do to avoid any reflection light on your glasses?
I didn't really get your explanation on inrush current. Could you clarify that?
Anybody know what the thermal camera model is he is using? or have recommendation for PCBs - which require being fairly close to the board and decent resolution. TIA
Do you have any tips for troubleshooting when you can't find the issue using the thermal imaging camera?
I've heard some people use a "smoke test" when first powering up a board. What are your thoughts on this method?
How do you deal with static electricity when working on a new circuit board? Are there any precautions you take to avoid damage?
What is the prompt for the thumbnail?
I tried following your guide, but my circuit board still isn't working. What could I be doing wrong?
If you have a short, just pour some rubbing alcohol on the board and watch for bubbles.
I've heard that freezing the board before powering up can help prevent issues. Give that a try.
If you suspect a specific component is causing issues, try removing it from the circuit and see if the problem persists.
If you can't afford a thermal camera you can use thermal film.
Lifehack
You can use alcohol or brake cleaner spray. The area where it evaporates first is the hottest. Thermal film is much less sensitive
@@AndruShows that's alright when you already know the specific problematic area is and just looking for the particular component. Alcohol disperses evaporates quick, not giving enough time to scan a larger area. Another alternative could be rosin atomizer
As an experienced engineer, I can confirm that thermal imaging cameras are a game changer for troubleshooting. It's definitely worth the investment.
What would you say is the most common mistake people make when powering up a new circuit board?
For beginners, don't bother with a thermal camera, just hold your hand over the board. Don't worry, time heals all wounds.
You didn't talk much about ESD precautions. You should have mentioned that more.
When in doubt, just reflow the whole board in an oven. It'll probably fix any soldering issues.
What is the most challenging circuit board issue you've ever encountered, and how did you resolve it?
The pacing of this video was too slow for me. I wish you had covered the material more quickly.
Step 0: Connect an electrolytic capacitor backwards on you bench PSU as a gift to the electronics Gods before power-up of the new board.
Hi.!
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This video was too basic for me. I was hoping for more advanced troubleshooting tips.
Do you have any tips for troubleshooting when you can't find the issue using the thermal imaging camera?