Is it necessary? - Page 1
Forum section: electronics / beginners

author: unknown1211
author_rank: Newbie
timestamp: May 16, 2021, 08:33:09 am
content: How To Sew Stuff Toys And Accessories For Your PetStuff toys are a source of happiness for your cats, dogs or any pet you have in your home. Like us, these animals want to have company and by the way, they love soft toys. To buy different toys for your pet is good but what if they don’t like it? All your money will be wasted and they are definitely not going to play with that toy. But if you have a skill like sewing then you can make a number of plush toys for your pet at home.If you have the best first sewing machine then just with the help of different tools you can create so many toys. It will cut down the cost as well as boost your pet's mood every day. These toys won’t take so much of your time in preparation.Here we are giving you some ideas about easy pet toys you can make in your home in no time. Don't forget to visithttps://craftsselection.comfor more helpful sewing tips and sewing machine buying guides.Little DoggieIf you are a beginner then definitely you must be wondering that this is going to be one of the most time-consuming projects because now you have to cut the fabric in the shape of small doggie. But we have come up with the solution and that is a print. Just print a picture of a puppy and keep it on the fabric. Cut the fabric in that shape by tracing a shape with the help of chalk first.Now cut down the image and pinned the fabric. Sew it all around, make eyes and all other things on the face. Keep one side open and fill the cotton from there. Make sure that little puppy is fluffy enough to make your pet feel happy. Present this to your dog and it’s going to be a super happy day for him.Play Tent For PetNo matter if you own a cat or a dog, they always love a tent where they can play and feel secure all the time. Take 5 dowels, a blanket or a long warm scarf, safety pins, and a thick cord of fabric. First, lay down double dowels perpendicularly and single parallel. It must be the shape of X. Tie them from the middle so it should be “X”. Now stand the structure and add two more dowels in it to support it.Now tie the blanket to the dowels from the middle in a way that the rest of the blanket must be on a floor. It should create a flap for pets. Use safety pins as well to join it strongly. Your cat tent is ready. If you don’t have a blanket or scarf then you can sew a blanket or scarf at home with the help of the best rated sewing machines for beginners.❖❖❖ Picked For You:Best Products For Sewing CraftsSelection.comHammockWhat will be the best way to make your angry or sad pet happy? Create a hammock for them. It’s super easy for you and you only have to sew the fabric in the shape of a hammock if you don’t have any in your home. Flip a table that is useless for you or in a store for a long time. Attach fabric from the ends with the help of hooks.Do this process for all four ends and make sure it’s strongly attached. Now it’s time to surprise your pet. Keep them in the hammock and push it gently so they can actually understand how it works. This is going to be one of the most amazing toys or accessories you can prepare for the pet.A Soft BunnyIf your pet loves to have a small and soft thing around them and they are as innocent as a bunny then here we are telling you about how you can prepare a bunny out of any t-shirt. You can make it any color and there is no need for shopping. All you need to buy is cotton to make it soft and super comfy for your pet.You don’t have to spend so much time cutting. Just print the shape of a bunny out from the printer and start cutting it. Once you are done with the cutting, Start sewing it. Fill the cotton inside and use buttons to create eyes. Use any fabric for the facial expression or to create the tongue of the bunny. You can use a number of bunnies or a big bunny for your pet.A Soft PillowWe all love feeling comfy all the time and when it’s time to sleep, it feels great to be comfortable in the bed. If you have already prepared the bed of your pet but now you want something more to make them feel comfortable or love their bed then sew the best soft pillow for them. Pillow is an easy thing to sew and you can make pillows for your bed as well.It doesn’t require a big complicated machine but you can make this easy and comfy project with the best inexpensive sewing machine for beginners.To make it more fun for the pet, make an animal or create a bear with a big tummy like a pillow. In this way, your pet may feel like some friend is with them all the time.Fill the soft cotton in your pillow and sew a straight line. Your pillow is ready in no time and hopefully, your pet is going to love it. It would be great if you will create an animal as per your pet’s choice so they can be actually thankful to you.➤➤➤ See Also:List of Top Sewing and Craft Machines CraftsSelection.comConclusionPets are definitely moody and none of us want them to be in a grumpy mood all the time. To make them happy it’s important to make sure they have things to play. Pets don’t like to feel alone and that’s why you should always sew something for them. It will help you in polishing your stitching skills and will make your pet happy.

author: tooki
author_rank: Super Contributor
timestamp: May 16, 2021, 09:02:43 am
content: That depends entirely on the amplifier you have selected. You can’t connect the speaker directly to the battery.

author: mindcrime
author_rank: Unknown
timestamp: May 16, 2021, 09:18:13 am
content: Can you explainexactlywhat you're trying to accomplish? Generally speaking, you wouldn't connect a battery to a speaker, so this whole request sounds very strange. A battery produces DC, so if you connect it to a speaker (assuming sufficient resistance to where you don't start melting wires), the only thing that would happen is a one-time click when the speaker coil energizes. After that, the whole thing would just lie there and do absolutely nothing until the battery dies. At which point it would continue to do absolutely nothing.

author: radiolistener
author_rank: Super Contributor
timestamp: May 16, 2021, 09:35:32 am
content: Rspk = 8 ΩPmax = 0.5 WU = 9 VImax = sqrt(Pmax / R) = sqrt(0.5 / 8) = 0.25 AmpsRmin = U / Imax = 9 / 0.25 = 36 ΩSince your speaker has 8 Ω, the minimum additional resistance required is:Radd-min = Rmin - Rspk = 36 - 8 = 28 ΩSo, you're needs to use resistor about 30 Ω or above.But not less than 28 Ω, because otherwise your speaker will be burned out.Also don't apply battery to the speaker for a long time, because it is designed to work with power applied for a short time.

author: Ian.M
author_rank: Super Contributor
timestamp: May 16, 2021, 09:56:10 am
content: A 1/2W 8 ohm speaker has a max rated current of 0.25A RMS. Its DC resistance is probably a lot less than 8 ohms. Therefore if you connect it to s stiff 9V voltage source (e.g. to check the phasing), you will burn out the voice coil. You need a total resistance of over 36 ohms to keep the current under 0.25A and avoid any risk to the coil. Even a humble zinc chloride PP3 is likely to have an internal resistance well under 36 ohms when fresh so may burn out the voice coil, and alkaline, NiMH or Lithium PP3 batteries have low enough internal impedance and short circuit currents high enough to bur out the voice coil very quickly if you don't use an extra series resistor. Beware of the resistor wattage required: a 33R one would need to be 2W or higher to survive 0.25A continuously. How much lower wattage you can go for brief connection depends on the resistor type and how long its got to survive for.Quote from: radiolistener on May 16, 2021, 09:35:32 amRadiolistener has misapplied his first formula. He's calculated 55mA current from 1/2W power dissipated in the speaker and series resistor combinedCalculate I correctly from P=I2R of just the speaker, then the rest of his methodology is correct.

author: radiolistener
author_rank: Super Contributor
timestamp: May 16, 2021, 12:17:32 pm
content: Quote from: Ian.M on May 16, 2021, 09:56:10 amYes, but if you apply 9 V to 8 Ω the current will be about 9 / 8 = 1.125 Amps. This is why there is needs additional resistor in series to avoid speaker burning out.Quote from: Ian.M on May 16, 2021, 09:56:10 amHm, technically it can be less than 8 Ω, because impedance is measured for higher frequency than 0 Hz. But as I remember I tested 8 Ω speakers and their resistance at DC was about 8 Ω. But I'm not sure now. Needs to check.In order to avoid mistake I suggest to measure actual speaker resistance at DC with multimeter.Quote from: Ian.M on May 16, 2021, 09:56:10 amyes, you're right, in order to get max current we're needs to use DC resistance of the speaker only

author: Ian.M
author_rank: Super Contributor
timestamp: May 16, 2021, 12:48:07 pm
content: We both agree a series resistor is necessary unless the 9V battery has a particularly high internal resistance. My only criticism of your calculations was your mistake calculating the maximum voice coil current the speaker can withstand. As your calculation gave a significantly larger series resistance no harm would have occurred, though it probably would have reduced the cone deflection to the point that phasing would be difficult to determine.N.B. When using P=I2R to calculate Imax, one must use the nominal 8 ohm speaker impedance, not its lower DC resistance.

author: radiolistener
author_rank: Super Contributor
timestamp: May 16, 2021, 12:49:27 pm
content: I fixed calculations.In any case it's better to use higher resistor in series to avoid damage

author: Zero999
author_rank: Super Contributor
timestamp: May 16, 2021, 01:41:57 pm
content: Why do you want to connect a speaker to a 9V battery? The only reason I can think of is to test the speaker, in which case I'd very briefly connect the speaker, to the battery, with no resistor, so see if it clicks.

author: Caliaxy
author_rank: Frequent Contributor
timestamp: May 16, 2021, 02:43:46 pm
content: Quote from: Zero999 on May 16, 2021, 01:41:57 pmThis^^^Quote* and hear

author: TimFox
author_rank: Super Contributor
timestamp: May 16, 2021, 02:44:40 pm
content: A very important point from above is that the DC resistance of a speaker voice coilmust be less thanthe audio-frequency impedance presented to the driving amplifier (what is meant by 8 ohms in the spec), since there is additional impedance from the electro-mechanical interaction with the air facing the moving diaphragm. The DC resistance is an inefficiency in series with the "motor" that produces useful sound from the device. That is why DC voltage can make an unsafe DC current in the coil when applied directly to the speaker for too long.

author: Zero999
author_rank: Super Contributor
timestamp: May 16, 2021, 04:18:24 pm
content: Quote from: Caliaxy on May 16, 2021, 02:43:46 pmLol, but come to think of it, looking at the cone move is a good test for polarity. The cone will move in, or out, depending on the applied voltage. It isn't important for a single speaker, but in a stereo, both speakers should be wired with the same polarity.

author: Ian.M
author_rank: Super Contributor
timestamp: May 16, 2021, 04:31:01 pm
content: OTOH you *should* be using identical speakers for stereo, so unless they are the lowest grade of 'china export' junk, it should be sufficient to simply wire to the same physical terminal positions.Where individual driver polarity does matter and cant be matched by simple visual inspection, is if there's different types of driver and a crossover network involved, to prevent undesirable notches at the crossover frequencies.

author: BeBuLamar
author_rank: Super Contributor
timestamp: May 16, 2021, 06:06:02 pm
content: I still don't know why the OP wanted to do it. If he wanted to see the cone moves then a 1.5V battery like AA or so would be better. The OP didn't want to come back and give us an answer. So sad.

author: Gyro
author_rank: Super Contributor
timestamp: May 16, 2021, 06:47:49 pm
content: Quote from: Ian.M on May 16, 2021, 04:31:01 pmRemember that the OP is talking about a 0.5W speaker, that's a small diameter transistor radio size.I would like to see some further clarification from the OP too - a clickbait title and no detail?

author: tkamiya
author_rank: Super Contributor
timestamp: May 17, 2021, 03:18:11 am
content: I thought we've all done something like this when being young and brand new to electronics.... I've done it.My answer is, yes, you'd need to have a register but:If you briefly connect speaker to 9V battery, it should tolerate it for a second or two. You'll hear "bomp!', see the cone move by pretty big amount and that's it. If you keep it like this, you'll burn up the speaker coil. You can have something like 50 ohm register or something, and you'll still hear it, and you can keep it connected for a while. But you won't hear anything.Before you start wondering, please do not connect it to mains house socket. There is a great deal of danger in this. As long as you'll stay with small batteries, the worst you'll do is damage the speaker. I'd just try it both ways, so you can see.