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  • andrewty commented on Khaleel123's instructable 3D Printed Arduino OLED Watt Meter1 week ago
    3D Printed Arduino OLED Watt Meter

    You could do with changing the title to include "DC Watt meter"You would need a multiplying function to calculate instantaneous I * V to generate a watt value.You can't just measure Irms and Vrms and just multiply. That excludes the load phase.Take a capacitor across the AC voltage. It absorbs virtually zero power even though the current is measured as significant mAac, or Aac.Same for an inductor. The reactive element of the load does not absorb power. Only the resistive part of the load absorbs power.

    you could do with changing the title to include "DC Watt meter"You would need a multiplying function to calcukate instantaneous I * V to generate a watt value.You can't just measure Irms and Vrms and just multiply. That excludes the load phase.Take a capacitor across the AC voltage. It absorbs virtually zero power even though the current is measured as significant mAac or Aac.

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  • HI-FI 4 Channel Audio Amplifier VERY Simple and CHEAP!!!!

    Have a look at the chip dissipation when delivering power to the 4ohms loads.The graph shows ~23W being dissipated when 1W is being delivered.the heatsink will need to be very large to get rid of 23W if you plan to have continuous average outputs of 1W into your loads.Look at the THD vs output graph.the signal distortion rises rapidly as the output passes above 15W It passes 0.1% THD when the output reaches ~18W into 4ohms when the supply has sagged to 14.4Vdc.The Absolute maximum operating voltage is specified as 18Vdc. Allowing for voltage sag at the supply pins makes this a quad 18W amplifier, not 40W.

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  • andrewty commented on 24Eng's instructable Power Drill to Belt Sander Conversion1 month ago
    Power Drill to Belt Sander Conversion

    A next to useless instructible."you'll need a 3D printer," What !

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  • Industrial Isolation Transformer From Trash

    the isolated supply feeds the Device Under Test (DUT).The isolated supply is NOT used to supply the grounded oscilloscope.Never probe anything with the scope probe deliberately ungrounded. or use the specialised differential probe that costs more than most scopes.

    Using two identical mains transformers back to back gives an output voltage that equals the input, when there is no load current.As soon a load current is demanded, the output voltage drops.The voltage drop under full power load is roughly two times the voltage regulation of the mains transformer.eg, using two 230:55Vac 8% regulation 500VA mains transformers will give a 1:1 input to output voltage on any EU harmonised supply when no load current is drawn.When the 500W resistive load is applied, the voltage will drop to ~inputVac/(1+0.08)² ~86% input Vac. This resulting isolated voltage is well below the minimum voltage specified for an EU harmonised voltage.

    I have to ask the same question.We have our newly boxed isolation transformer. It has a 3pin plug top ready to plug into the mains wall socket. It has a 3pin output socket. It has an MCB on the input and another MCB on the output.How do we wire up the Protective earths (PE)?Do we wire the enclosure to the PE?Do we wire the output socket to the PE?Do we fit a GFI (RCD, RCBO) to the input wiring?Do we fit a GFI to the output wiring?

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  • Designing a Dual 40A PWM Speed Controller for Brushed Motors

    Are the gates to Q1 & Q3 (Pchannel mosFETS) drawn upside down?

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  • How to Make a Command Prompt Defragmenter in Windows!! (works for All Versions of Windows)

    I try to download the 11steps, but the screen just refreshes and shows step 1 with the comments following on.I tried using the "view all steps" icon but it does the same taking me straight back to showing step 1.What's wrong?

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  • andrewty completed the lesson Class Overview in the class 3D Printing Class2 months ago
  • How to Make Mini CNC 2D Plotter Using Scrap DVD Drive, L293d Motor Shield & Arduino

    where are the instructions.Many pics but no details to manufacture the mechanisms.Not much about how to control the electronics.

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  • How to Remove a Stuck Nut (without stripping threading)

    WD40 is not a good lubricant for non rusty threads. WD40 is pretty poor as a penetrant.Use a penetrating lubricant formulated for that duty.many better suggestions in the earlier comments.

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  • Control Your Home Appliances Using Arduino And Relay

    For, connecting the AC bulb to the relay properly:Connect live wire from AC wall outlet to Common port on relay and one terminal of AC bulb to Normally open terminal of Relay. Then, Connect the other terminal of AC bulb to GND on the AC wall outlet.NO !!!!connetc the other terminal of Mains bulb to NEUTRAL, not to GND.

    For, connecting the AC bulb to the relay properly:Connect live wire from AC wall outlet to Common port on relay and one terminal of AC bulb to Normally open terminal of Relay. Then, Connect the other terminal of AC bulb to GND on the AC wall outlet.NO !!!!Connect the other terminal of Mains bulb to NEUTRAL, not to GND.

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  • andrewty commented on emills05's instructable How to Make a UTP Cable 3 months ago
    How to Make a UTP Cable

    the critical part is crimping the RJ onto the cable ends.But the pic is so bad that I can't see any detail !1 out 10

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  • andrewty commented on Victor805's instructable Drill press for ~$203 months ago
    Drill press for ~$20

    How good are the drawer slides at holding an accurate Up/Down motion?

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  • andrewty commented on mikeasaurus's instructable Corner Lamp3 months ago
    Corner Lamp

    Tungsten filament lamps run very hot.Fluorescents run a lot cooler.LED lamps are cooler still.Most can be touched without burning ones fingers.The exposed heatsink is usually the hottest part you can touch and it needs to be cooled to ensure a long life for the LEDs. They do not tolerate heat.A bit of air circulation helps, as does a big surface area to transfer heat to the surrounding air.

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  • Salvaging Pure Silver BNC Connectors

    Is the black a corrsion product of the silver?How do you convert that back to silver?Other wise the silver gets thinner, until there is no silver left !

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  • andrewty commented on kidNeutrino's instructable Toughening a RFID Door Opener4 months ago
    Toughening a RFID Door Opener

    How you do send a signal to pull the door handle?

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  • andrewty commented on KeystoneScience's instructable Easy High Voltage Power Supply4 months ago
    Easy High Voltage Power Supply

    Could you explain the operation?

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  • andrewty commented on DerpyCyclops's instructable Easy Infrared Detector4 months ago
    Easy Infrared Detector

    What is the other component on the plug in board?I can see the IR receiver at the top and the three lead out wires at the bottom.

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  • H-Bridge for Dummies: How It Works and How to Make Your Own

    Could add some information on timing?How fast can they be switched with the controller?

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  • andrewty commented on Nematic!'s instructable Capacity Test of Fake 186504 months ago
    Capacity Test of Fake 18650

    Yes.You must take account of the voltage.Were the four batteries in series, or in parallel, or in a series parallel arrangement?Without this bit of information we cannot follow your analysis.

    10400mAhr ?Why milli-amperes?It would be more comprehensible to state 10.4Ahr just like any other big battery.We are all used to evaluating the Ahr of car and leisure batteries. I recently bought a 22Ahr 3.7V lion battery pack.With that info I can see immediately that it is a big battery and what output voltage to expect. I can see that if I draw 1A it is likely to last ~22hours.

    10400mAhr ?Why milli-amperes?It would be more comprehensible to state 10.4Ahr just like any other big battery.We are all used to evaluating the Ahr of car and leisure batteries. I recently bought a 22Ahr 3.7V lion battery pack.With that info I can see immediately that it is a big battery and what outpyt voltage to expect. I can see that if I draw 1A it is likely to last ~22hours.

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  • How to make an Universal DC Motor Speed Controller

    if your motor is 5A thenthe mosFET must have a current rating exceeding 15A (3 times the normal maximum current)the irf530 has a max cold rating of only 14AThe 540 is much higher IdOr use a low Rds on type eg irlu8726 max I=80A and Rds on < 0.006ohms for best efficiency and cooler operation.

    a ¼HP 12V motor will draw a lot of current. And even more when starting.Use a very high Id device with a very low Rds on.The example I gave above irlu8726 might do the job, or irfb3607 80A, 0.009ohmsAt 3 times the running current you will need a rating of >50A mosFET. 1HP=746W, ¼HP=186.5Wrunning current is ~186.5W/12V = 15.5A 3times that is ~47A ratingThe 555 timer will need a driver to charge up the gate capacitance. This becomes a much more onerous design.

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  • andrewty commented on HoracioP3's instructable LED bonding manually4 months ago
    LED bonding manually

    the Ultra violet is dangerous to eyes.Will this exposed LED emit enough UV to damage our eyes?

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  • DIY Homemade Constant 5V Voltage Source

    remove your instructible and read all the others.Try reading the datasheet.

    I agree, this instructable is full of mistakes.The writer just does not understand how to get a 5V output.The LED could have been used as a minimum current load for the lm7805 series regulator. Some datasheets state that the minimum current should be 5mA and a few state 10mA minimum.Using a series resistor to limit the LED current is mandatory.For 5V out and 1.8Vf for the LED you need a resistor value of (5V-1.8V)/0.01mA = 320ohms, use a 330r for near 10mA min draw, or use 680r for 5mA min draw.If one decides they need reverse polarity protection then one can use the forward diode on the output. But we need to compensate for the forward voltage drop by adding a similar diode into the GND (labeled 2) of the regulator.The Vf (Vdrops) of the two diodes won't be identical, but close enough ...see more »I agree, this instructable is full of mistakes.The writer just does not understand how to get a 5V output.The LED could have been used as a minimum current load for the lm7805 series regulator. Some datasheets state that the minimum current should be 5mA and a few state 10mA minimum.Using a series resistor to limit the LED current is mandatory.For 5V out and 1.8Vf for the LED you need a resistor value of (5V-1.8V)/0.01mA = 320ohms, use a 330r for near 10mA min draw, or use 680r for 5mA min draw.If one decides they need reverse polarity protection then one can use the forward diode on the output. But we need to compensate for the forward voltage drop by adding a similar diode into the GND (labeled 2) of the regulator.The Vf (Vdrops) of the two diodes won't be identical, but close enough to achieve the USB 5V supply voltage.

    Agreed.This instructible is a complete waste of other Builders' time.It is a "how NOT to" ruin a useful idea.Read the lm7805 datasheet to see how to do it properly.

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  • andrewty commented on ThomasJ1's instructable Simple Vault Mechanism4 months ago
    Simple Vault Mechanism

    Please do a couple of instructables for telescope making.Can't get the reply to work so adding comment here instead.

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  • Learn To Do Aluminum Sand Casting

    acetylene is too hot for melting aluminium.Propane is plenty hot enough.Oxygen is also too hot.A good propane/air burner will melt lead and aluminium.But probably not cast iron. That needs quite a bit more heat. Oxy/propane is probably OK for cast iron.

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  • Converting a Quick Release Vice Into a Regular Vice

    We had quick releases on my school benches (4 off and over ten years as teacher). They never gave any trouble.I have one at home on my woodwork bench. It too has been totally reliable.Some manufacturer (not in the UK) must be making a codswallop of making bad clones.

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