Voltmeter using MAX1496

All the controls are connected to a 10pin FRC which is to be hooked to a microcontroller to automatically set the ranges. RJ1 and RJ2 controls the LED drive currents. They are made as female pin headers to insert resistors. More details will be added soon…

Datasheet : MAX1496, MAX1447, MAX1498 datasheet

The post Simple Voltmeter schematic using Maxim’s ADC with LED driver appeared first on My Electronics Journal.

Last month I got another 1Gb strip to the already outdated Compaq C770TU laptop. Things didn’t go very well as transcend now ships modules with 1Gbps chips instead of the older 512Mbps chips. So now my laptop randomly fails to boot unless I press some key. Here is a small video of me tweaking around with it.

[youtube]http://www.youtube.com/watch?v=Wj3mA0Kizhk[/youtube]

Coming back to the programmers, I now have two of them. The USBPICProg one and the OpenProg. Although I have used my USBPICprog many times, I didn’t get a chance to use the new one. In the mean time, here is a picture of the two programmers mating

USBPICPROG and OpenProg , OpenProg has got a USB type B connector while USBPICprog just has broken Sony phone data cable

The broken Sony Erricson USB cable was the only one available at the time I built USBPICPROG. On the OpenProg the USB type B is not sitting on the mainboard because of the difference pitch. OpenProg firmware was burned into the PIC18F4550 using USBPICPROG.

The Adapter board is used to program PICs, all of them 40, 28, 20, 18, 14 and 8pin.

The adapter board just allows to plugin all types of PICs into one single ZIF socket. More about both of these programmers will be coming in detailed posts.

The post USB Microcontroller Programmers and Laptop RAM appeared first on My Electronics Journal.

Here is the picture Murugesh sent me (All the copy rights or copy lefts belong to Murugesh )

PWM IC CG8010DX1 - SMPS chip used mainly for Desktop PCs

The IC turned out to be a PWM IC used for PC Switch mode power supplies. while composing the post on SMPS circuit diagrams, I had actually came across a circuit with this particular IC, but ignored for it being not so popular. But the guys at edaboard even posted a link to that circuit diagram.

Circuit diagram of PC SMPS using IC cg8010dx16

Downloads

I have downloaded and attached the datasheet of IC CG8010DX16 – PWM controller.

The post PWM chip CG8010DX16 SMPS schematic and datasheet appeared first on My Electronics Journal.

LTSpice schematic of a simple op-amp voltage follower based Linear Voltage Regulator.

Downloads

Op-Amp_linear_voltage_regulator SPICE files

The post Op-Amp based voltage regulator tutorial and SPICE modelling appeared first on My Electronics Journal.

The new Extech ex430 true RMS multimeter

The post New multimeter – Extech EX430 appeared first on My Electronics Journal.

So why not a Switching PSU instead of the Linear one?

• I have zero experience designing a switching power supply
• I do not have a ‘properly’ working DMM
• Linear one is much easier to build and I had components lying around
• Although I haven’t yet designed any Linear PS, I was pretty sure they would work real good

And off I went got a piece of paper and started scratching my head!

Linear Power Supply constructed using an op-ampFully assembled power supply. The heat sink is pretty big, but its no match for the large amounts of heat the transistor dissipate.

The scribbled diagram is not correct. It's purpose was to get a basic idea to work on.

Theory:
The series regulator is a simple extension of the voltage follower circuit of an op-amp. In simple words, an op-amp always tries to adjust its output so as to make both the inputs equal (inverting and non inverting). (the concept of virtual ground is used here). Since an op-amp cannot provide much current a series dissipative element, an NPN transistor, is used. The one I used is a 5Amp TIP122 Darlington transistor.

If we increase the bias to the base Vbe of an NPN transistor voltage drop across it Vce decreases (as Vbe increase, Vce decrease). When the whole circuit is wired up and if the output voltage increases due to some reason, this should be compensated by an increased voltage drop across the transistor (Vce). For this the base bias Vbe should decrease. This means the output voltage should be multiplied with a scaling factor and negatively fed back to the base of the transistor. This is where the op-amp comes to play. The output through a potential divider is connected to the inverting pin of the op-amp.

To get a stable output voltage, we need a reference source to compare the output voltage to. For this purpose, a simple Zener diode and a series resistor is used. This acts as a pretty good reference source. The reference voltage is connected to the non-inverting pin of the op-amp. This is because, we need to get a positive correlation between reference voltage and the output.

5A NPN darlington Transistor TIP122-D

The post Design : Linear Voltage regulator using Op-Amp Voltage follower appeared first on My Electronics Journal.

The problem being with the fan was kind of obvious. And off I went, grabbed a screw driver and kept taking things apart until nothing was left to fall out. The heat dissipation system is interesting. A large Copper bar is pressed on to the processor and this runs along the inside of the body to the air vent. There, a window with fins is attached to the copper bar (the fins are probably Aluminum but I am not sure). This is at the exit of the centrifugal blower. The pictures will help in easier understanding.

The fan is held by just one screw. After the fan is just pulled up, the heat fins connected to the copper bar coming from the processor can be seen. (The copper bar is also seen here) This is clogged with dust.

I have already removed a small mass of dust and lint from the blower side of the fan. This is a centrifugal blower.

The blower and the fins fitted on the heat bar was full of dust and this prevented the blower from rotating. A large painting brush was used to remove the dust. The blower was connected to 5V supply and tested. The sound is really good to hear. especially when it is outside. Blower has a rating of 320mA @5V. Opening the laptop is pretty much easy if you have got the right tools. Most of the time a Philips screw river and a flat one would suffice. The flat one used to unclip the tabs. Only thing you need to care is not to break any of the clips and not to loose any screws you take off.

The post Breaking in – Compaq C770TU laptop appeared first on My Electronics Journal.

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When I had a couple of them lying around, I cracked them open and after a few days, fixed some of them. It was actually much easier done than said. But one bad thing about SMPS repairs is that there aren’t any good resources out there on the web. (OK may be there are, but I failed to find some). That is why I decided to make a series of posts with my repair notes, schematics and stuff I have learned through opening those bricks. Being the first post, this is the schematic post. You can grab the schematics available on the net here. Please send me a link if you have found a new schematic and I will add it here.

The Schematics

There are two circuits commonly available for PC ATX SMPS.

• Based on IC2003
• Based on KA7500
• Based on TL494 and  LM339

KA7500 and TL494 are pin to pin compatible PWM controllers. There are only minimal differences in their specs. The major difference being for the TI one TL494 DTC offset voltage is 0.1V where as for KA7500 it is 1.2V.

Thanks goes to : http://electro-tech.narod.ru

SMPS schmatic using IC2003. The cheap Chinese SMPS uses a circuit based on IC2003. The EMI filter and output filters are usually left out, and the components heavily underrated. The schematic is hard to find, not drawn by me.

This schematic along with the low quality parts is normally seen in Mercury branded SMPS. I have 6 of those lying around. All with blown caps and no EMI filter. EMI filters are not much of a concerns usually for ratings below 350W. But a good engineer /designer will always add an EMI filter.

The manufacturer has omitted this along with output filter coils to cut costs.

Here is an SMPS based on IC2003 after repairs. I found some inductors to add to the output filter, but couldn't find any for the EMI filter at input.

SMPS schematic using IC KA7500

The TL494 LM39 combination was the most widely used one till recently.

Click on the images to enlarge. If you know anything about Switching Power supplies, the schematics are quiet obvious. They are simple. Include simple protections and have very few components.

Datasheets

TI PWM controller datasheet – TL494 | Fairchild PWM controller – KA7500C | National’s Quad Comparator – LM339

Links

Product page of TI’s TL494 | Product page of KA7500 | Product page of LM339

The post PC SMPS schematics with IC 2003 and TL494 appeared first on My Electronics Journal.

SMPS repairing

I have about 6-7 computer power supply lying around. Two my own, one from a friend, and the rest from a computer shop of my neighbor. All are broken and most of them are crappy low cost ones. They usually have a common schematic that is widely available on the new. Here is the schematic for those who have yet to find it. Since the SMPSs are from different timeline, the degradation of quality is profound. The first ones used rather good quality capacitors and the input had a connector and fuse holder. The later generation ones have got some of the worst Cps I have seen, does not have the input connector and the fuse is soldered directly to the PCB. And last but not lease, there is NO EMI filter!

I am all for low cost, but cost cuttings should always come after quality assurance. And this is exactly why I hate places like India and China. we build the cheapest and lowest quality goods, throw them away once it breaks down, thus increasing the resource usage and littering. This is why low cost products suck. I will write more about the SMPSs later.

All I did was replace all the electrolytes with some quality ones available. I was pretty sure it was the electrolytes because one was blown and electrolytes in SMPS are famous for dying an early death. Everything went fine, I shorted the Green (Power ON’ ) pin to GND (Black) and voila, it just powered up. Always feels great to see things work.

Canon dissection

My digital camera is a Canon A710IS brought from the UK (my sister bought when she went to UK). I grabber a screw driver and finally opened it up. And it was rather neat. I have some PICs. All are extremely low quality since they are from a webcam.

Canon A710 IS LCD and buttons.

Canon A710 IS lens, AF assist and motor.

Canon A710 IS Lens closeup

As expected, the design was brilliant. I always admire the people who design enclosures, products. There is certain amount of sex appeal for a well designed and assembled product. And I am a fan.

Earthing.

About 4-5 months ago, my PC Power Supply, motherboard and HDD got damaged. It didn’t occur to me that it could be a ground fault. Ground faults are famous for causing RAM damage (I do not know the truthfullness but it seems so). But when the New SMPS that I installed also was damaged, I thought about the earth connection. And, it turns out, our electrician had done an amazing job of earthing – 2 feet 1/2 inch GI pipe driven to earth connected to the Mains ground by a 1mm copper wire. If he was around when I found this out, I would have shot him. WTF was this. A 1mm single strand copper that is more than 100ft total would never carry much current. So I decided to do a new earthing myself. In the end I have about half a meter square pure copper sheet burried with three 4mm copper wire connecting it to the mains ground. The total distance of this from my PC has also been reduced greatly.

The final connection was made only today, and now I need to power up my PC after a looong time. All this time I have been working on my laptop. Powering up the PC means I can get much more involved in electronics, mainly because it would provide a ready RS-232 port and a full table to work on.

The post Repairing an SMPS, taking apart my camera and Earthing appeared first on My Electronics Journal.

Last day, edaboard changed their layout. The new one is crappy and is pretty hard to use (for me). The main reason I was on edaboard was because it had an easy to use interface. Everything was right on you face. The one and only thing I look for in forums (other than the member base) is the interface. Send me a message if you know some good forums on electronics.

The post I am out of edaboard appeared first on My Electronics Journal.