Small Projects... ( long ) - Page 1
Forum section: electronics / projects

author: jackbob
author_rank: Regular Contributor
timestamp: October 16, 2011, 07:04:19 am
content: On my spare time I enjoy making small little projects Just on a small piece of FR4 board. I am only 15 years old with a serious passion for electronics so don"t criticize too muchThe boards I designed and made all myself, they are nothing amazing just fun little projects to teach me more and give me something to do. I buy my parts in bulk online for use in many projects then some pieces of FR4 and I hand solder all of them. The oscilloscope opened up in the background is in another topic. Sorry for the picture quality again, it was in the dark and with a 1080x1920 resolution. The first one is a pwm generator based on a 555 timer and has dip switches to change frequency range with the pot. to change duty cycle. The second picture is a board that will allow you to control 120V power with 5v TTL levels like an arduino, it uses triacs and optocouplers and has a missing heat sink on one triac, being used in another project currently. The third board is just an lm317 voltage regulator with 6 lm317's and a fine and course micro pot to adjust voltage. The close up of the mosfet is part of a small pwm motor control I built but I will use the same mosfet x20 in my upcoming project. The heat sinks on the large fets for the Pwm board are also being used in another project. The last board is an 8x8 led matrix ( still haven't got around to writing the arduino code for it). If you're still reading this you are amazing and thanks for looking,Jacob.

author: Conrad Hoffman
author_rank: Super Contributor
timestamp: October 16, 2011, 07:44:14 pm
content: It took me a lot more years to get where you are right now. Good work!

author: shadewind
author_rank: Frequent Contributor
timestamp: October 16, 2011, 07:51:38 pm
content: Very well done! You're going to get far. Once you start laying out proper PCBs, it gets even more fun since you're not so limited by what packages are available in through hole versions as well

author: jackbob
author_rank: Regular Contributor
timestamp: October 16, 2011, 10:51:40 pm
content: The Internet is an amazing resource which allows me to learn at rapid speeds. I want to start making pcb's different because I end up using jumpers and soldering them like this really limits how much I can fit on a board. I'm starting to build a 500 amp pwm motor control and am still using fr4. It's going to be a challenge to make solder tracks that will handle the current and it's going to take many rolls of solder. My school gave me some lead free solder because the thickness was too big but I'm not a fan of lead free. I hope this projects works because it's going to take a lot of time and I have dumped a lot of money in parts so far. If I end up getting mystery smoke or a fireworks display I won't be happy at all, especially on a project this size.

author: IanB
author_rank: Super Contributor
timestamp: October 16, 2011, 11:12:10 pm
content: I think you are over-using solder in those constructions. Solder is intended as a filler material, not a conductor in its own right. It's going to get expensive for you to keep using solder at that rate.Look for a spool of tinned copper hookup wire and use that to lay your tracks, using just enough solder to tack it down and connect to the component leads. For short connections the excess length of bent component leads should be sufficient.

author: Unknown
author_rank: Unknown
timestamp: October 16, 2011, 11:25:23 pm
content: Well done! Keep following your passion.Quote from: IanB on October 16, 2011, 11:12:10 pmThat's an excellent exercise to develop a feeling for how quickly heat propagates in the solder

author: shadewind
author_rank: Frequent Contributor
timestamp: October 16, 2011, 11:35:44 pm
content: Quote from: jackbob on October 16, 2011, 10:51:40 pmJust a note, it's the material in the board which is called FR4, not type of board itself. What you probably mean is a prototyping board. FR4 is used in most custom PCBs as well.

author: jackbob
author_rank: Regular Contributor
timestamp: October 17, 2011, 12:05:21 am
content: FR4 is quicker and sounds cooler. I will make this next projectwith fr4 and solder because I already bought the material. But making 500 amp rails out of solder... Might be cheaper to make it with gold. I looked at pcb routers which are relatively cheap for what they do. I found them on ebay. Well screw a car now I know what I'm getting instead. The board made by the router looks fantastic but doesn't look capable of high current. I haven't had a close look at one but I don't think I would push more than 30 amps through one. Anyways thank you for all who supported me. The eevblog is now becoming an addiction, I am on here all the time. It's great to have people who actually understand me and can help me. I am a relatively new member and have posted tons already ( I am dominating ) haha. Dave deserves a reward or spot in the history book for creating the eevblog. It's the next facebook for EE's.Thanks again,Jacob.

author: IanB
author_rank: Super Contributor
timestamp: October 17, 2011, 01:48:40 am
content: Just to give you some context, here is a 500 A rail:If your conductor has a resistance of 0.01 ohms and you pass 500 A through it, the power dissipation will be 500 x 500 x 0.01 = 2.5 kW. If you happen to live in the USA, the maximum power you can draw from a 120 V outlet is 1.8 kW. In that case your losses would be greater than your available power, but you would have a great room heater (or fire starter).

author: jackbob
author_rank: Regular Contributor
timestamp: October 17, 2011, 04:06:00 am
content: I might end up using copper busses soldered to the board but this will not be running on wall power haha that would not go down well. I will probably test high current at 12v and I have a sub panel that will deliver 100 amps at 240v. I don't quite understand what your calculations are or what you are trying to say but 2.5 kw doesn't seem right for losses in the conductor. Could you explain in more detail? I have a pretty good understanding of what I'm doing for the conductors because I have a power inverter which has 150 amp rails. If I'm not understanding something I should know before I build these rails. Thanks,Jacob.

author: 8086
author_rank: Super Contributor
timestamp: October 17, 2011, 04:17:39 am
content: 100A at 240V?Most houses (here at least) have a 100A breaker/fuse at the power inlet for the whole house. Somehow this doesn't sound like the best idea

author: IanB
author_rank: Super Contributor
timestamp: October 17, 2011, 04:21:38 am
content: Quote from: jackbob on October 17, 2011, 04:06:00 amI'm basically saying you are not going to have 500 amps in a home build construction. It is beyond reasonable limits for an operating current. To give you an idea of what 500 amps means, your bus bars to carry that current would have to be copper rods 0.5 inches in diameter, and switching it would require components and heat sinking of a size far beyond what is available to the home constructor.What the linked photo was intended to show was that 500 amps is the kind of current you find in electric traction supplies for trains, and the gear to handle that current is enormous and heavy.Broadly speaking, what my calculations were trying to show is that conductor size is roughly proportional to the square of the current. So in going from 150 amps to 500 amps everything basically has to be ten times bigger. Circuits that electronically switch 500 amps are built with big metal lugs, bolts and copper cables as thick as ropes. (With powerful fans for cooling.)

author: jackbob
author_rank: Regular Contributor
timestamp: October 17, 2011, 04:55:37 am
content: I have all that. It's a motor controller for a vehicle ( I plan on a go kart ) but it won't be 500 amps continuous, just for seconds maybe 20 seconds continuous. It will run off batteries to power the motor. I have a topic called "pwm MOSFET driver" which goes into much more detail. I have massive heatsinks and serious 24v blowers which push air like no tomorrow, they are also working with push pull fans on each end of the heatsinks. I will start a new topic for the project when all the parts come in.Jacob

author: IanB
author_rank: Super Contributor
timestamp: October 17, 2011, 05:23:28 am
content: Well, you asked about the 2.5 kW. It's like this. If you have 500 A flowing through a conductor with a resistance of 0.01 ohms then by Ohm's law the voltage drop will be 500 x 0.01 = 5 V. And therefore the power loss in that conductor will be 5 V x 500 A = 2500 W, or 2.5 kW.The general problem here is it is really hard to eliminate resistances from a circuit to get the whole thing down to the milliohm level and therefore avoid those power losses.Usually what you do to increase power beyond a certain point is to increase the voltage, otherwise the resistive voltage losses will spoil your day.

author: IanB
author_rank: Super Contributor
timestamp: October 17, 2011, 05:31:37 am
content: Quote from: jackbob on October 17, 2011, 04:55:37 amAh, I remember that. You are talking about switching 150 V and 500 A with MOSFETS. IMHO that's getting seriously into the realms of power engineering, with enormous potential for expensively destroyed components if you get the tiniest thing wrong. When you have 75 kW flowing through your circuit, you only need 1 or 2 stray kW to escape and you will not be talking magic smoke, you will be talking magic fireworks. Very exciting flashes and bangs

author: jackbob
author_rank: Regular Contributor
timestamp: October 17, 2011, 06:09:05 am
content: That's the type of electronics I like. I love power electronics such as inverters, converters, pwm, vfd, smps, amplifiers, and things that have to do with power. I'm not too much into small electronics but am gradually going to that area as I need to in order to properly contol the large power electronics. I have had more fireworks shows than I would like to admit but those were not carefully planned or designed. I have had mosfets turn into speeding bullets.. Trust me they will explode. I always stress safety when building big projects with large amounts of power. Most testing during build will never go beyond a few amps but when I finish I will test it good ( the moment of truth). I probably won't even use 500 amps most the time, it's just good extra room if I need it. It will probably be around 200-350 amps most of the time .. Which is still slot of power. I understand your calculations now and they are right. That's a huge loss and such a small resistance. Thanks,Jacob.