555电容器测试仪

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Introduction: 555 Capacitor Tester

About: I miss the days when magazines like Popular Mechanics had all sorts of DIY projects for making and repairing just about everything. I am enjoying posting things I have learned and done since I got my first to…

这个is something I built from a published schematic late in the 1980s. It works very well. I gave away the magazine with the schematic because I believed I would never need it again and we were downsizing.

电路围绕一个555计时器构建。这些非常便宜且非常可用。我始终紧张地通过在焊接时涂过太多的加热来破坏半导体,因此我使用了8个引脚插座并将其焊接到位。然后我将555个定时器芯片按到插座中,当焊接完成时。

这张照片显示了我的测试。我钻洞1/8 inch Plexiglas to make a circuit board. Just decide where each component should be located and mark the location for the holes. Drill with a small drill. I place the component on top of the Plexiglass and connect leads below the Plexiglass. There is a selector for different resistance arrays. I tapped the Plexiglass for 8-32 brass screws. I soldered leads to the screw heads under the Plexiglass and I attach an alligator clip to the appropriate screw for the desired resistance range on each test. I used hot glue to fasten components to the Plexiglass where necessary. The battery holder is fastened to the Plexiglass with a screw.

Step 1: Removing the Mystery

I know just a little about electronics, but not a lot. For a long time I was in awe of the genius who used a 555 Timer chip to make a capacitor tester. Then I began reading a little more about 555 Timer circuits. According to my rudimentary understanding, they can be configured in different ways, including astable, monostable, and bi-stable. Each works a bit differently with different results for different purposes. After reading about each of these just a little, I decided the capacitor tester I built is a very common monostable multivibrator or “one-shot” configuration.

A monostable multivibrator turns “on” when a momentary contact switch is depressed and released. The multivibrator produces a continuous pulse that lasts until the capacitor in a resistance/capacitance bridge charges up to a particular percentage of a full charge. When that happens, it signals the 555 Timer chip to stop the pulse. In this case, that means an LED came “on” when the momentary contact switch was depressed and released. It continued to be lit until the capacitor charged to its threshold level. Then the 555 Timer turned the LED “off.” If the resistance has been carefully chosen, counting the number of seconds the LED was “on” indicates the value of the capacitor multiplied by 1 or by 10 or by 100 according to the selected test range.

这个link在电路摘要中,使用555定时器芯片讨论单稳态多谐振荡器电路中的电阻/电容桥,它给出了用于计算LED在秒内的标准公式,基于指定的电阻和指定的电容。它还提供了用于使用555个定时器芯片的配置的示意图。如上所述,R1和C1是变量。在我的测试仪上,如果R1为900,000欧姆,则乘法因子是1.如果R1为90,000欧姆,则乘法系数为10.如果R1为9000欧姆,则乘法系数为100.在我用来推出100微米时的照片中的照片在观察极性的同时,电解电容器到测试鳄鱼夹。LED在10秒内出去了。选择器设置在10x选项上。10 x 10 = 100.电容器的值非常接近其指定值。(该测试仪不表示其他东西,如电容器的内部电阻。)

The image is a monostable multivibrator circuit from the link above to Circuit Digest. You could build the circuit as shown. R1 and C1 are conveniently marked. I would add a three-position selector for the resistances mentioned in the paragraph above. It would make the tester easier to use.

第2步:我的电路

As I mentioned, I did not save the magazine with the schematic that I built, but gave it away. I have looked, but not found anything exactly like it on the Internet. I believe any monostable multivibrator circuit would work. They seem to vary just a little.

I did try to trace the circuit from my actual tester. It can be viewed in the photo with this step. I viewed my circuit board from the bottom and tried to trace the connections accurately. There is always the possibility I made an error, although I checked it a few times.

I am accustomed to pin out diagrams on IC chips that begin with #1 in the upper left corner and progress to pin #2 and so on. See the circuit diagram in the image from the previous step. Pin #1 is on the bottom at the center. What you see in that diagram is now the standard way to show the pin out for a 555 Timer chip. My diagram of what I built is further complicated because the pin out is from the back side of the circuit board.

看看second photo。请注意555计时器上的闪亮圆形区域。它表示PIN#1。PIN#2低于它。右下角是PIN#5。PIN#6高于它。PIN#8位于右上角。

Step 3: How to Use the Tester

包含电路图的磁带杂志,没有关于如何使用它的信息。我必须通过审判和错误来解决这个问题。该测试仪适用于较大尺寸的电解电容器,通常为10微小渣和更大。它将适用于低于1微米的电容器。

注意9伏电池连接。当我完成时,我总是取下电池并在我想使用测试员时安装它。鳄鱼夹已连接到黄铜螺钉以选择范围。鳄鱼夹已被连接到正在测试的电容器上。LED是“开启”,测试正在进行中。

1. Always discharge the capacitor first.

2. Select the appropriate resistance range. (If you are testing a 4700 microfarad capacitor counting 47 seconds makes more sense than counting 4700 seconds to arrive at the approximate value of the capacitor.)

3. Attach the positive (+) and negative (-) test leads to the capacitor. Be careful to observe the correct polarity.

4. Depress the momentary contact switch and release it.

5.计算LED熄灭直到LED的秒数。乘以选择电阻范围的适当因素。

Good capacitor—The LED stays “on” for the appropriate number of seconds before turning “off.”

Range set too high—The LED turns “off” as soon as the momentary contact switch is depressed and released.

Capacitor is “open” and must be replaced—The LED turns “off” as soon as the momentary contact switch is depressed and released.

LED stays “on”—The capacitor’s connection to the tester is the wrong polarity, or the capacitor is shorted and needs to be replaced.

第4步:你需要这个吗?

关于我发现用电容器测试仪电路的杂志我买了一个40岁的Zenith Trans-Oceanic AM-Shortwave Radio,用真空管构建。当我开始使用收音机时,电解电容器开始吹一个,并且当时使用它很有一点。测试可疑电容器而不是仅在无线电时刻在无线电时抛出金钱和新电容器是有帮助的。该测试仪帮助我识别出故障的电容并改变它。我不再拥有那个收音机,但偶尔我发现当我尝试再次工作时检查电容非常有用。我不经常使用这个测试员,但是当我需要它时非常有用。我现在确实具有多米的电容秤,但米经常不涵盖所需的范围。我通常建造的测试仪。

图像是通过互联网监控时间。它非常像我所拥有的收音机,但不是它的照片。

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    33.Discussions

    0
    西班牙船长

    8小时前

    See Elektor magazine July/August 1977 "Digital Capacitance Meter with 555 Timer" by J. Borgman .

    0
    craneman

    1天前Step 4

    如果你name that magazine, I probably have a copy of it.

    0
    w88.com

    1天前回复

    谢谢。I think it may have been Electronics Experimenter’s Handbook, or something like that, maybe Electronics Experimenter. It would have been from late in 1988, I think. I do not think it was 1989, but that is not impossible. It was not a monthly, but perhaps a quarterly. I think I remember a light gray cover with black letters and a yellow banner. We gave away a bunch of things to a resale store to benefit Habitat for Humanity. Recently I found all of the Popular Electronics magazines I gave away. They are on-line as downloads, but I did not find the one with the 555 capacitor tester. The “article” is only a couple of inches high in the middle of a page. I think the magazine offered something like 100 basic circuits to build.

    0
    craneman

    15小时前回复

    Thank you, I have many of the older Popular Electronics, and a few of the Nuts N Volts magazine.
    Some of the online archives will allow a search of the database.
    Cheers

    0
    w88.com

    15小时前回复

    谢谢。我相当肯定是1988年晚期的电子实验者手册的副本。我发现几个副本在线上存档,作为PDF和其他人出售,但不是我拥有的。这是一种流行电子产品的出版物。我认为可能已经使用的电路可能出现在早期的流行电子产品中,我已经将这些杂志下载回到1985年,但尚未找到我使用的原理图。我确实发现电容器测试仪,基于在单稳态模式下配置的555的电路有点类似的电路。该电路没有带有电流限制电阻的LED,但是它将链接到示波器或计数器。我很高兴知道是什么让我的测试人员工作,并能够分享我与其他人一起学到的东西,他们学到了那些希望有一个廉价的电容测试仪,即使它没有给出内部电阻,即使它也不提供内部电阻或泄漏信息。

    1
    pgagen

    2 days ago

    Hownice to see. As a young engineer I built this as my default tester 42 years ago. Nice to see builds with the 555 timer still going in this microchip world.

    0
    w88.com

    回复2 days ago

    Thank you for affirming that it works. I like low (or lower) tech. solutions to problems. A young person at an office supply store was helping me find a refill cartridge for the Fisher Space Pen. He had never heard of them. I told him the story I had heard that we in the USA spent thousands of dollars developing a pne that wrote upside down in zero grsvity. The Russians simply used a number 2 lead pencil, instead.

    0
    Johnc430.

    2 days ago

    how do you accurately count 47 seconds?

    0
    w88.com

    1天前回复

    到目前为止,我不需要计算到目前为止。这是一个插图。但是,我没有使用定时设备。相反,我只计算1 - 一千,2 - 一千,3千。它足以准确,特别是,由于电容器可以少得多或者比指定的更多,并且很好地完成工作。如果您想知道,我读到了电子教科书中的那个。

    1
    lee78

    1天前

    Here's a simple 555 circuit (NO circuit board, 1 resistor, 1 LED, 1 earbud)

    https://www.uchobby.com/index.php/2007/05/29/lm555-tick-tick-tick/

    that will tell you the capacitance of the capacitor if you use an oscilloscope.

    "
    You can use this circuit to figure out the value of the capacitor, if you know precisely the value of the resistor. Display the ticks on an oscilloscope and measure the time between ticks. 137 beats per minute is .44 seconds between ticks, a frequency of 2.28 Hz. Capacitance in farads C = 1.44/(R*Hz). So (if my resistor were exactly 27000 ohms) the capacitor labeled “20 mFd” actually was 23 microfarads.

    。000023 = 1.44 / ( 27000 * 2.28)
    "

    Cheap digital multimeters will tell you the precise value of the resistor.

    0
    diykiwibloke

    2 days ago

    Thank you Phil. Nice tutorial. I guess one could also use "dead bug" construction for this.

    0
    w88.com

    回复2 days ago

    I did not know the term “dead bug construction” and had to look it up. That is what I used to reconstruct the schematic of the copy I built. I might rather build it on a breadboard first. There is still room for very human mistakes, even though it appears simple. Thank you for looking and commenting.

    0
    Electronflyer1.

    2 days ago

    这让我想到了。如果你有一个柜台,你可以像一个涩,然后有数字阅读。也许是要将读取读取值的图表。你应该努力。

    0
    Johnc430.

    回复2 days ago

    是的。好主意。你应该在那个!

    0
    w88.com

    回复2 days ago

    我喜欢阅读和试验电子产品一点,但远远超出了我的水平。谢谢。

    0
    HParker5_63

    2 days ago

    I am thinking , this with a counter would be able to test my farad capacitors. All of my new cap testers have an upper limit so testing the super caps of 1, 2, 5, farad is not an option. A counter would be needed for these large caps. This would be a good go-nogo basic test.

    0
    w88.com

    回复2 days ago

    Some web pages I have seen related to using a 555 Timer with large capacitors suggests inaccuracies in the expected results appear beyond a certain point.

    I built a similar cap tester in the 80's and I still use it. The one I have uses a radio shack analog meter movement which goes up to a certain number on the scale and stays there as long as the button is pressed. There are a number of switchable scales which go from 500pF full scale to 50 uF full scale. I also have that Zenith Trans Oceanic that you show in the photo. In my opinion, that's the nicest of them all. I think it's 1950 A600 model.