Assembled and boxed Clone PI AVR metal detector

Some more photos of boxed Clone PI AVR metal detector and self made coil.

I have made a coil from Ethernet cable between two round plywood sheets filled with Makroflex sealant. More about making coil from Ethernet cable can be fount here. Idea how to seal everything came from here.

Clone PI AVR intself was boxed in a box I bought in local electronics store. I decided to add a switch to switch off external beeper so that sound will be provided only through headphone socket. For the coil connector I have selected some two pin microphone connector. I think in general it came up pretty well.

Will be mounting everything on appropriately bent and painted PVC pipe. Will post pictures later. Some day. Probably.

Clone PI AVR back panel
Clone PI AVR back panel ( external sound on/off, coil and power switch )
Clone PI AVR front panel ( buzzer hole, headphone socket, lcd and controll buttons )
Clone PI AVR front panel
Clone PI AVR internal layout with batteries
Clone PI AVR internal layout
Self made detector coil for Clone PI AVR

UT61E digital multimeter schematics and integrated circuit datasheet

Uni-t UT61E Multimeter - Circuit diagram

ES51922 application circuit for ES51922 datasheet.

ES51922 application circuit.png

In UT61E 1some features of ES51922 are not used and can be enabled by simple hardware diy:

112 APOSEL I Idle time selection for auto power off feature.

58 SLEEP O Sleep mode indicator, asserts low in SLEEP mode.

105 BKOUT O If BKLIT function is enabled, this pin will change from –3V to +3V
For 60 sec, once press BKLIT pin again within 60 sec, this pin will
Change back to –3V

102 BKLIT I Back light function. Pulse low to set BKOUT pin output.

113 BKSEL I Set to V- to change the backlight idle time from 60 sec. to 180 sec.

UT61 series Operation manual.



Adjusting and calibrating Hameg HM-605 channel gain

Yesterday I have noticed that voltage or gain of channel 1 in my scope is a little bit off ( noticed that by analyzing one circuit on same output with dual signal ). I have Hameg HM-605 service manual (you can download it at the bottom) and I found there instruction of adjusting channel gain. Basically you just provide square wave signal ( I used scopes calibration output ) and adjust corresponding pot. Its an easy fix as you can see in a video below.

Download HAMEG HM-605 oscilloscope service manual here.

And users manual in English.

Getting cheap oscilloscope on ebay

As casual electronics tinkerer I have always wanted to add an oscilloscope to my tools collection but never did so. There are many reasons why, for example, oscilloscopes are expensive and you don’t want to spend a huge amounts of money on thing that will be used just occasionally and basically is a “toy”, or, for example,  I have never owned one and there are gazillions of them and I was not sure which one or with what specs should I get. You can have modern digital ones, older analog, cheap Chinese DSO’s, PC scopes etc. Those Chinese DSO`s are tempting, but finally, one video from EEVblog convinced me that I should probably look for decent old analog one:

So, after this video, I have started looking for an old analog scope, dual channel, 20MHz and up, known brand. Some looking here and there revealed that I probably will not get a scope for 20 bucks, at least not here in Europe. Starting price for more or less decent ones was somewhere about 50 Eur. One day on I have noticed HAMEG HM605 for sale. Starting price 50eur, seller says it has some triggering problems.

hm605 bid.png

Some investigation revealed that this is the kinda decent scope and usually is more or less easily fixable. That was it, decided that 70eur was top price for it, made a bid and finally bought it for 65eur. Whoohooo! It arrived after a week or so and the first test showed that everything works ok except correct triggering as it was stated by seller. Luckily my assumptions were correct and I could fix it without huge efforts. You can read about fixing it here.

So, here I am, proud owner of HM605 analog oscilloscope that I plan to use for some time. It works like a charm and is a huge help for me while learning the art of electronic, literally 🙂

Image result for learning the art of electronics

Repairing HAMEG HM-605 oscilloscope trigger problem

Bought used HAMEG HM605 oscilloscope with trigger problem. Tested it with sine wave and yes, cannot trigger it nor with automatic trigger neither manually. Decided to resolder all contacts near the trigger switch. Luckily it was easy accessible, just had to remove cover. After resolder next test revealed that sometimes trigger works, and sometimes not. Just a slight touch (no pressing) on external trigger button seems to be cause. So I resoldered all the contacts of ext trigger switch and some around and triggering started working as intended. Fixed.

Signal Differentiation and Integration

Good explanation about Differentiation

“The output wave of a DIFFERENTIATOR CIRCUIT is ideally a graph of the rate of change of the voltage at its input.”

High Pass Filter or Differentiator

Fig.8.4.1 The Differentiator Circuit

Fig-8-4-2.gif Differentiation

Fig 8.4.2 Differentiation.


And Integration

“The shape of the input wave of an integrator circuit in this case will be a graph of the rate of change of the output wave ”

“The low pass filter circuit is therefore called an integrator only when:

a. The input wave is a square wave.

b. The periodic time(T) of the input wave is much shorter than the circuit time constant(CR) i.e.(T<=CR).”

Low Pass Filter or Integrator

Fig. 8.5.1 The Integrator (also low-pass filter) Circuit.

integration.gif Integration

Fig. 8.5.2 Integrator Action