Savel brain dump in English!

LC meter based on LM311 and PIC16F84 micro controller. 0.0pF – 1uF and 0.0uH – 0.5H range. Quite precise meter.

My Machtech tester is capable of metering the capacitors, but is very complicated to measure short lead capacitors, not speaking about SMD ones. Also, I needed to measure the coils. In www.sprut.de I found some LC meter schematics. It was quite interesting and capable to measure very small values. It is based on the LC generator frequency difference when additional capacitance or inductance is attached. The only precise element in the meter is capacitor. Also, it is possible to use trimmer and set the meter to required level of precision.

The meter is based on LC generator on LM311 and microcontroller PIC 16F84 (16c84). The indicator- standard alphanumeric LCD display. From old Hagenuk cable detector I removed very nice LCD displays with big numbers and symbols. They are as twice as big as normal. The internal jumper JP1 is used to switch meter from nanofard mode to microfarad. It is useful for old schoolers 🙂

The meter under the construction:

Original schematics are in the author pages.
Preview of the schematics:

I’ll place this meter and other stuff to standard 19″ rack from some old switch. There is original PSU from the switch. It gives me all needed voltages and is quite powerful.

According to mine idea there will be: LC meter, frequency meter, wide range high frequency functional generator with sweep option.

Lithuanian only blog entry.

Abstract:

I decided to change front fenders for my car. As they are not original, I needed to try if they fit to the car. So one weekend was committed for car repair.

All you need is 3 spanners (wrenches) with metric size 8, 10 and 13. Also philips screwdriver and old blunt knife.

(please wait, it is 600kb animation)

First of all, remove grid with logo of the VW car. It is connected only with plastic retainers (fixers). Then, use wrench number 10 and remove bumper. Pull it to the front ant remove. Do not forget wires- disconnect them.

Now remove plastic protection under the fenders. They are screwed to the body of the car by several screws. Original are number 8, if repaired- then typically replaced with philips type.

Now you can remove the fenders. They are bolted to the body of the car with number 10 bolts and screws. 4 in the bottom and few on the top. One bolt is number 13- where capote is grounded, near antenna. If fender is original, it is glued to the body. Use knife here.

The beginning was the damaged battery from my old video camera. The old battery for it was made from 6 (six!) NiMH cells. The cells were worn out and didn’t hold too much charge. Full loaded battery was emptied in 40 minutes of filming. Also, my mother managed to short circuit the battery and everything finished with lots of fumes and explosions. The original battery for mine camera is very expensive as camera is very old and quite rare. Now I needed to build new battery using cell bought from shop. There is two type of cells which can be used in my battery: NiMH and Li-ion.
I needed either 6 cells of NiMH technology or two of Liion. (Original battery is Li-ion). The price for both types of cells are quite high. The project was closed for a while. Recently I received few batteries from notebooks. They are build in circa 2005 and the cells are quite good. The batteries where discarded due to typical problem- on cell failure. The battery is 14.8V and 4400mAh. Inside there are 8 cells. So the battery organisation is 4×2 and cell is 2.2Ah.

Next stage- proper Li-ion charger for double cell battery. I digged few types of mobile phones, but all of them had only one cell charging controller. The controller is typically made by Benchmarq (now Texas Instruments). From good people, I received two sample chips for dual cell charger. It is BQ2057. And it was very good that I receive two chips. The first chip was damaged during construction. The schematics or the circuit diagram is typical, from datasheet. The transistor I used is from old HDD controller, some PNP, 2A one. Thermistors were from notebook batteries.

The circuit was working, but as it is linear regulator, quite a lot of energy are waisted on regulating transistor. As wall plug is giving about 15V and the current is quite big for 2Ah cells. The transistor is getting very hot. So from old scrap I removed switching mode power regulator (from old LCD monitor stand). It is LM2576-5 (fixed output voltage). I attached trimmer to feedback circuit and regulated output up to 9.4V (assuming that voltage drop on power transistor is about 1V and the battery need to be charged to 8.4 or 8.2V).

Both PCBs were glued together to one small unit. In the upper photo, on the left you can see the charger. I charged 5 pacs of cells. But one morning I found my charger dead- there was hole in the BQ2057 chip. I measured all the voltage around the chip and everything was in normal. It is quite mystical failure. Now I am waiting for new chips and I’ll try to build better charger. (hoping to receive switch-mode charger chips with “all included” version).

I was testing radio link in our city and with mine country house. The testing transceiver was Kenwood TK-760G-1. I am a bit disappointed with the quality of radio link.

The frequency of radio is about 132? ~ 174 MHz. The output power is up to 25W. The transceiver was in high power mode and the antenna burned the hand quite well. The output stage of the radio is built using Mitsubishi RF module M67741H. The output power of the module in 150 … 175 band range is 35W when powered from 12.5V PSU. Inside the module there are two transistors (or maybe amps) and few passive elements. According to diagrams in datasheet, the module maybe can be used in FM band with transmitter like Veronica.

I was using simple quarter wavelength antennas. The link quality was poor. Even when I attached special external antenna placed on the roof. Meanwhile the radio link using old soviet transmitter was ideal. Ant the output power of Маяк (164MHz) transceiver is only 10…15W. Maybe the reason of it is the sensitivity of receiver? Bur in old radio it is about 0.4 … 0.8μV, while kenwood states 0.25 … 0.33μV. It is strange.

One more interesting moment- old soviet transmitter can be tuned to 0.2μV sensitivity and up to 50W (!) output power without changing components.

Now I need to reprogram Kenwood to other bands and test again. Maybe the used frequency is jammed? I soldered RS232 to TTL converter with MAX232 chip. Also found special software in the internet. While programing I receive “-PC-” on transceiver display and lot of errors on PC. Someone told, that kenwood PC link is very lame and I need to use old PC and exact cable like original one from kenwood. Damn capitalists- they use lame hardware to make user to buy original cables. Hundreds of dollars for fucking few transistor cable…

This Lithuania only blog entry. Just about that I found lots of wild hemp growing near my horse house. And my dog just tore the pillow.

Cannabis sativa, also known as hemp, is a species of Cannabis. It is a dioecious, annual herb. It has been used by humans throughout recorded history for its fiber, for its psychological and physiological potential as a source of drug material, and for the nourishment and oil of its seeds.

Mad dog

Due to some national holidays we had four free days. Ant the mother nature decided to show us some heat. In the shady spot it was about 30°C, ant the thermometers on the sunny side were “overloaded”.

Reader must understand, that Lithuania is quite cold country. The 22°C temperature is called “hot”. And quite rainy. So such hot is rare and dangerous. Ant it is wet hot. The hygrometer placed inside the “sealed” house is showing more than 80% of humidity.

And now some reminiscences from some not very old times, January 20, same year. This image is from Henkas blog and is about five months old:

In short- about 70 degrees of temperature swing.

I found nice VFD display on one 5.1 surround sub-woofer. It was quite big, powerful sound system with some indicator to display signal spectrum. I removed indicator and become suspicious- the device was too simple to be real. After looking to VFD without color cover, I discovered that it is just cheap Chinese imitation. From the first sight it looks like real device:

But if you look to VFD, you can find that indication elements are connected in strange way- the spectrum of the signal is hard-coded to VFD:

The PCB is very simple- only three LM324 quad operational amplifiers and bunch of resistors. Theoretically it can generate 12 levels of indication, but VFD is only with 9 anodes. Schematics are typical- comparaison of input signal with voltage divided by resistor network. When I feed-ed DC signal to the input I received nice “spectrum” of it.

Also, I like the mystic word “REVEL”. It looks like some “right” version of word “LEVEL”. This is nice illustration of Chinese-English vocabulary.

Next time, buying “cool” surround speaker system, be careful.