Wiring Digital Voltmeter Ammeter Without Shunt

I have this:  http://www.ebay.com/itm/271210262267?ssPageName=STRK:MEWNX:IT&_trksid=p3984.m1439.l2649. They say is can it be used up to 10 amps without a shunt, but I can't find wiring diagram. I am trying to wire into 50 watt led light. I know the small red and black go to power source. I am not sure how to connect 3 thick wires( red, black, yellow) without a shunt. I am only trying to meter 1.5 amp circuit.  Here's what I am trying to wire. Thank you

Posted by flatfish 4 years ago


voltmeter and ammeter

Hi guys, could someone help me with this thing,

Posted by mammotz 7 years ago


I have continuity in both coils (AC-DC) but no power output?

I have a 12v 2A transformer without power outputI testes/checked with a voltmeter both coils (AC-DC) but no V+ output

Posted by MarcosM117 4 months ago


variable load DC volt meter?

I would like to build my own one of these with more settings and variable load and input voltages. Maybe someone has a more elegant solution? Something that would fit in a small box or maybe even a something to put in between the DC source and my multimeter Voltmeters

Posted by Menthol 8 years ago


test a power wupply without a voltmeter

OK so yesterday i got this broken laptop from someone.  I knew the problem was the ac jack ( it would charge if the the jack was proped up in just the right way) but only if I used a power supply that did not come with the computer.  I have never soldered anything in my life but figured what the heck.  I took the laptop apart and located the AC jack.  Since I do not have the cash flow to buy a new AC jack I decided to experiment and just reflow the solder on each post of the jack. Well things went well.....I think.  The problem is this.  When I plug in the power supply the "charge" led comes on for just a second or two and shuts off right away.  But there is further information about this power supply.  It is putting out 3 volts less then the original power supply.  Could this be the cause?  The think the OEM power supply is dead because I have nver been able to get the computer to do anything with that one.  Is there a way I can test this power supply without a volt meter or any other product to plug it into?

Posted by jcaresheets 7 years ago


Problem with my variable regualted dc power supply.

I have a used variable voltage regulated power supply that does not work ; when i turn it on, the Volt meter tops, and if I switch to ammeter, it shows 0amp, if i plug a voltmeter on the female banana plugs there's no juice... I've checked the fuse, it is not damaged. i've also checked to potentiometer with my ohm-meter looks like it's working normally. I don't know what is wrong with it... Do anyone have any idea ?

Posted by lordofthedonuts 9 years ago


Really small analog gauge controlled by simple circuit

I'm looking to make a steampunk version of dr who's sonic screwdriver with some LEDs, a tiny recording module for the sound, and I also wanted a little analog gauge with a needle that would activate when the button was pushed. It doesn't have to actually measure anything, I just want the needle to move in some way. i found a little voltmeter on sparkfun that I could probably repurpose, but it's 2x2 inches which is a little bigger than I wanted.  I'm looking for something about half that size. Does anyone know of anything that would fit the description, or a way I could fake it?

Posted by sasham43 5 years ago


Measuring LED Voltage

Greetings... I have quite a few "salvaged" LED's, none of which have I the slightest clue as to their voltage. I have attempted to measure them using the diode setting on my voltmeter with dubious/mixed/questionable results. Although the measurements are momentary (the reading is barely of sufficient length to note), I can usually arrive at a value. Unfortunately, when I repeat the measurement on the same LED the reading is invariably different. For example, I just measured the value of a random LED (green) and came up with the following: 1.3. 1.4, 1.8, 1.6. I've rounded the values to the nearest decimal point. Are these values through voltage? Are the differences between the readings significant or should I use the minimum when calculating resistor values? I'll, no doubt, have a few more question later on. I appreciate your elucidation on this matter... Best to all, hassi

Posted by hassi 10 years ago


Help with Viewfinder Pinout??

Well guys, I've had this viewfinder sitting around in a drawer for TOO long. I ripped if off an old camcorder in the dump like 2-3 months ago, remembering a few different projects I've seen on here (and other sites) such as: https://www.instructables.com/id/Super-Nightvision-Headset-Hack/step3/Disassemble-the-Viewfinder/ (sorry the hyperlink part of instructables never works for me) I know I've seen a project somewhere online too where a guy used one of these TINY crt's for a miniature arcade machine, just to name an example. I've ran into a bit of a wall here though, it would seem as though everyone else's viewfinders have indivigual wires coming off the board for power and video input. Mine doesn't, it has ONE ribbon connection (although mangled a bit, I still have the ribbon cable that goes with it). This is a really simple looking circuit board, but as I don't exactly have lab quality tools sitting around, I don't wanna solder wires onto it until I know for sure which is for power, I'd hate to fry it on the first time! I tried following the traces on the board but I've never been too good at that, is there some way I can probe around with a voltmeter to determine what is for video input and what is power? I've tried googling numbers off the board and tube and that didn't help either. If anyone can help me power this tube, please tell me!!

Posted by Punkguyta 8 years ago


Why does my LED lamp have AC voltage from case to ground and is it dangerous?

Here's the deal:  3-section under-counter LED light strip in an aluminum housing, with a 2 wire AC cable and plug for 220v. I found however, that when I set a voltmeter to AC and measure between the case and a ground (water faucet, natural gas line or the ground from an electrical socket) I get 74 volts with one unit and 89 with another. The seller first pointed out that a grounded cable should be used. I replied with pictures showing the unit is built to accept only two wire and comes with a two wire cord. Then they said using a sink as ground didn't truly represent ground and that the measurement was faulty and that the current is not dangerous regardless.  I took additional measurements using an electrical ground and the metal pipe from the natural gas line. Same result. However, I'm having trouble measuring current. I put the probe into the ten amp side, set the meter to the mA/A position and got nothing, although I did hear a buzzing sound emanating from the lamp housing--that can't be good. I then put the probe into the mA socket and tried again.  Same buzzing, no reading.  My questions: 1. What's wrong with my setup that I see no current measurement.  2. Is this a dangerous lamp? I took the one near the sink down. The other one is not within reach of an accidental grounding, so it is up until I'm ready to return both units. -Bob

Posted by bobcov 3 years ago


Help me fix ma zune!

I've got to fix this damn zune, there's no warrenty on it and all in all it's a piece of crap. The guy doesn't care that much if it can't be fixed. I've got shit webcam reference pictures. You'll see that the battery has the terminals connected to a small IC board with 3 solder pads on it, and a voltage regulator of some sort on the bottomside of it. The ribbon cable has 3 little metal spades that solder to those pads on the battery. There's voltage coming out of the pads (I don't have a voltmeter, just a tongue but that works just as good). When I've got the ribbon cable soldered to the battery and I touch the end of it to my tongue I can feel current, so why is it that only once in a while I get power to the zune? Like if I wiggle the cable around sometimes I can get a low battery symbol to come up and then it shuts off. I don't know why it's still showing a low batt symbol because I charged it and it feels like there's a good charge in there so what's the problem? I wanna get this fixed so I can play around with it, no I've never had the pleasure of a zune :p. Thanks guys for anything you can help me with. I was thinking maybe the IC came loose from soldering/desoldering the cable a few times, but it still appears to be stuck on the board pretty good. Well look at the pictures and decide for yourself. It's starting to look like I'll be buying a new battery, which apparently the ipod 30/60 gig batteries are the same size/amperage and can be used in the zune and at a low price of $14, I can probably get a battery that'll last longer than the factory one eh?

Posted by Punkguyta 10 years ago


PCB Repair Process of 3 different kind of circuits

1 Power Supply Circuit: During the circuit board repair process, power supply part should be inspected at the first hand and then come to the other part. +/-5V, Power supply failure can occur under below several situation: (1) NO power supply voltage or power supply voltage is deficiency, NC system is often used +/-5V, +/-12V, +/-15V and +/-24V, a few of them use +3.3V, and the varied or unstable voltage of power supply will cause the system working impropery; (2) Use voltmeter to test the voltage of power supply, and the result show is normal. Voltage waveform detected by oscillograph has shown the existence of big ripple. This situation maybe caused by open circuit of Filtering capacitance, bad rectifier diode or cold soldering, but sometimes it could be caused by an overloaded component which has been brokendown and damaged by power. (3) System can run properly when it is just being opened, after a while of operating, the voltage begin to drop off. This is usually caused by voltage stabilizing circuit and large power triode. (4) The voltage decrease accompany with temperature increase maybe cause by component cold soldering, it is electrical connection can be affected negatively when the temperature high up. (5) NO power supply voltage or supply voltage decreases significantly will cause the system to interrupt or stop working, this fault can be detected and spotted easier. (6) When the capacity of power supply load drop off or filter circuit become invalid, it will cause the system halt suddenly, this situation which is very difficult to justify can bring damage to the equipment and facility even get personnel wound. 2 Clock Circuit: Clock circuit mainly exist on the systematic motherboard, it is the foundation of large-scale integrated circuit system through which it can work, it can generate the constant square signal in the circuit base upon the crystal oscillator (commonly known as crystal), Once the crystal oscillator stop working, it is same as the heart of human being stop beating, the whole system will fall into the status of paralyzed, only after crystal can work under normal condition, the systematic circuit can operate under the command of CPU according to the frequency of crystal. The number and frequency of the crystal could be different due to the variety of numerical control system, but generally will at least one crystal, different clock frequencies required by the other circuit can be solved by frequency dividing circuit or other crystal. Crystal possess a higher rate of failure or damage, below are some malfuntions of crystal: (1) Leakage: Use multimeter and switch to P*10K level to test it, if the resistance is infinite, then it can be viewed as normal; (2) Internal OPEN CIRCUIT: Value of resistance is infinite tested by Use multimeter, can fail to generate oscillating pulse in the circuit; (3) Alternative crystal: Due to the transformation of crytal will cause its internal parameter change which can only be detected by osillagraph or cymometer. Although the crystal can still has oscillation, but the clock frequency is deviated from its nominal value, and the still existing oscillation pulse can’t make system circuit work properly due to the value of oscillation is wrong. Only cymometer can test its tolerance now. (4) In clock circuit, the both ends of crystal would be connected to ground by one ceramic capacitor value range from several picofarads to tens picofarads, failure of the clock circuit result from this capacitor leakage, deterioration is also more common. The best tool to test whether the crystal is good or bad could be oscillagraph or cymometer, multimeter is very difficult to detect the root cause. 3 Reset Circuit Reset circuit also exist in the circuit system of motherboard, it is unique set of large-scale digital integrated circuit. Microprocessor and interface circuit are all possess reset terminal. Reset pulse generate by reset circuit will clear the progam counter, force CPU recall the orginal files from the memory, execute initiation process on all the controller chips, system will occurs the phenomenon of disorder or crash as a result of faulty reset circuit, the method of using cymometer to illustrate the reset pulse is turn on/off power supply repeatly, observe and record the pulse value at the right moment of power supply on/off since it should be the normal square wave-form. If there is no existence of reset pulse, all the resistor, capacitor and transistor in the reset circuit should be detected. The reset terminal of integrated circuit should be regular low or high electrical level, or else, it is probably the malfunctional reset circuit or damaged integrated circuit.http://www.circuit-engineering.com

Posted by circuiteng 7 years ago