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A simple workshop generator m.cz.

żarówka rtęciowa 5382 33
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  • A simple workshop generator m.cz.

    Hello,

    Necessity is the mother of invention, sometimes the right equipment is needed for servicing, such as a low-frequency signal generator used to repair amplifiers and receivers. There are a lot of devices on the market, both new and used, but their price is unacceptable to me. So I thought that in order to save costs I would build something like this. The choice fell on a simple sine wave generator with three frequencies: 100 Hz, 1 kHz and 10 kHz, powered from the 230 V mains. I found a description of the electronic circuit on the Internet. It comes from the popular magazine Elektronika Praktyczna 1/95.

    The mechanical construction consists of a base made of steel sheet with two sides riveted to it. The lid is also cut from the same material. The metal pieces were cut with a hacksaw and then bent with a vice in my dad's garage. On it, the power supply is screwed with M3 screws through distance sleeves a few millimeters long. The front panel is made of plastic. On the latter, the so-called a small chassis with a generator board, a dependent isostat switch with frequency selection RC elements, a control lamp and a BNC output socket. The inscriptions were made with a thin waterproof marker. Before final assembly, the steel parts were painted with anti-corrosion paint. The box is permanently connected to the PE conductor of the power cable.

    The modules on the boards are connected by thin wires. The power supply includes a TS2/14 domestically produced transformer and a rectifier with a Delon doubler equipped with two filtering capacitors. From it comes the DC voltage of approx. 14 V and the alternating voltage of approx. 11 V to power the control lamp with the telephone bulb. The boards were etched in a solution of sodium persulfate heated indirectly by solar energy, the process for the power supply circuit took about 40 minutes. The Wien bridge generator contains a double TL082 operational amplifier placed in a socket. The first stage produces a sinusoidal signal with the selected frequency, the second is a buffer. A 60V/20mA telephone bulb is used to stabilize the amplitude, and the Telpod CN-15 cermet potentiometer is used to set it. The signal is regulated by a Telpod SP 1.2 carbon potentiometer from zero to approx. 4 Vrms. On the back there is an output ground switch.

    The approximate cost is a dozen zlotys and is low due to the use of recycled materials and parts, e.g. a three-core power cord with a plug is made of electronic scrap, the casing sheet was purchased at a local scrap yard, and the plastic is recycled. The rest of the used parts I had from my own stock. The elements that I bought myself are a mains transformer in a stationary store, two electrolytic capacitors (TME) low-SR Panasonic 470 uF/25 V/105 °C and a double operational amplifier TL082 (Allegro). Due to the shortage of some parts, work on this device took about one year.

    I add some photos of the project:

    A simple workshop generator m.cz.
    A simple workshop generator m.cz. A simple workshop generator m.cz.
    A simple workshop generator m.cz. A simple workshop generator m.cz. A simple workshop generator m.cz. A simple workshop generator m.cz.

    Cool? Ranking DIY
    About Author
    żarówka rtęciowa
    Level 37  
    Offline 
    żarówka rtęciowa wrote 3752 posts with rating 310, helped 359 times. Live in city Pelplin. Been with us since 2005 year.
  • #2
    CosteC
    Level 38  
    żarówka rtęciowa wrote:
    On the back there is an output ground switch.

    The switch is visible in some photos, and in others it is not. BNC is also ordinary, not isolated, so it is at PE potential - the same as in most function generators. So what does this "output ground switch" do?
  • #3
    żarówka rtęciowa
    Level 37  
    Hello,

    CosteC wrote:
    The switch is visible in some photos, and in others it is not visible. BNC is also ordinary, not isolated, so it is at PE potential - the same as in most function generators. So what does this "output ground switch" do?

    The switch is designed to break the ground loop when the output ground of the generator is connected with the tested circuit and the analog oscilloscope, in which its input socket is is permanent connected to the PE (protective) conductor. The photos were taken at different times.
  • #4
    CosteC
    Level 38  
    żarówka rtęciowa wrote:
    The switch is designed to break the ground loop when the output ground of the generator is connected with the tested system and an analog oscilloscope, in which its input socket is permanently connected to the PE (protective) conductor. The photos were taken at different times.

    Can you make some diagram because I don't understand. I have, perhaps mistakenly, the impression that the ground loop break is in the wrong place.
  • #5
    Mateusz_konstruktor
    Level 33  
    żarówka rtęciowa wrote:
    The box is permanently connected to the PE conductor of the power cable.

    And what about the mains fuse?
  • #6
    żarówka rtęciowa
    Level 37  
    Hello,

    Factory-made Polish devices with these transformers, e.g. power supplies for radio receivers or emergency lighting modules. they have no mains fuses on the mains supply side. So there is no need to use them in my design.

    As for the ground switch, I will soon draw and post a diagram.
  • #7
    CosteC
    Level 38  
    żarówka rtęciowa wrote:
    Factory-made Polish devices with these transformers, e.g. power supplies for radio receivers or emergency lighting modules, do not have mains fuses on the mains supply side.

    And what happens if the transformer gets a short circuit of, say, 200 ohms and starts to heat up to the point where it can ignite?

    I still don't understand what the switch does. Can you make a drawing?
  • #8
    prosiak_wej
    Level 38  
    CosteC wrote:
    I still don't understand what the switch does.


    I believe it cuts the PE wire from the mains cord from the housing.
  • #9
    pawlik118
    Level 31  
    CosteC wrote:
    BNC is also ordinary, not isolated, so it is at PE potential - the same as in most function generators.

    The front panel is made of plastic - it is non-conductive.

    Added after 1 [minutes]:

    I like. A reasonably maintained compromise of aesthetics to the amount of work.
    It is neat and looks decent.

    From what I remember, the fuse at the transformers, up to ~2.5VA, is not required. Perhaps this is due to the fact that the very thin wire of the primary winding is not able to carry the current that would give off power that could burn the insulation between the primary and secondary sides.
    e.g. Breve on their products
    gives the fuse value https://www.tme.eu/pl/details/tez6_d_6v/transformatory-do-pcb/breve-tufvassons/tez6-d230-6v/
    Does NOT provide fuse value https://www.tme.eu/pl/details/tez2.5_d_10.510.5v/transformatory-do-pcb/breve-tufvassons/tez2-5-d230-10-5-10-5v/?brutto=1¤cy=PLN&gclid=EAIaIQobChMIi5eS0dD1_wIV5AuiAx0 VSwghEAQYAiABEgIZSPD_BwE
  • #10
    CosteC
    Level 38  
    pawlik118 wrote:
    From what I remember, the fuse at the transformers, up to ~2.5VA, is not required. Perhaps this is due to the fact that the very thin wire of the primary winding is not able to carry the current that would give off power that could burn the insulation between the primary and secondary sides.
    e.g. Breve on their products

    I don't know such a recipe... It would be very strange, besides it assumes that there will be no magical failure anywhere else in the device that could lead to a fire..
    The fuse has two roles - protection against fire and protection against electric shock, of which it protects against electric shock only in specific cases - because depending on the position of the plug, the fuse can be on the neutral line.
    pawlik118 wrote:
    The front panel is made of plastic - it is non-conductive.

    I don't see it, the author can confirm/deny. I think it's October...
  • #11
    123104
    Level 12  
    The author wrote: "The front panel is made of plastic."
  • #12
    CosteC
    Level 38  
    123104 wrote:
    The author wrote: "The front panel is made of plastic."

    I'm honored, yes. I missed it.

    Still somehow I feel bad without a fuse ... Indeed, a wire in a tiny power transformer should not fall out of the transformer and strongly limits the current ... But could not a short circuit inside the primary winding heat it up too much? Modern transformers often have a thermal overload fuse for this purpose.
  • #13
    pawlik118
    Level 31  
    I'd probably give a fuse, just to feel good. Some time ago, an older colleague, a designer, told me about the "lack of its requirement" in small transformers, and it concerned certified medical equipment (2VA transformer). It sounded convincing then. It would be worth checking, for example in Breve :)
  • #14
    acctr
    Level 29  
    żarówka rtęciowa wrote:
    60V 20mA telephone bulb is used to stabilize the amplitude,

    Why this tension? Have you checked its characteristics for voltages equal to the amplitude present in the generator system?

    Moderated By Mirek Z.:

    Don't lower the level of the forum! You really don't need to write redundant posts.

  • #15
    prosiak_wej
    Level 38  
    pawlik118 wrote:
    The front panel is made of plastic - it is non-conductive.


    A board made of foamed PVC?

    As for the fuse - recently I have been resuscitating Carel controllers from Liebherr MediLine freezers. The controllers have a converter, which is an independent module on four legs. There is no fuse in the controller itself, I don't know about the converter - it is flooded with resin. I got one driver that got flooded from the outside. The plate was fried until the protection in... the laboratory's installation worked. Also, even if the converter had its own fuse - it would be of no use, because the manufacturer of the controller did not give anything.
  • #16
    ^ToM^
    Level 41  
    Nice product.
    I made such products myself somewhere in the 80s, following the example of Maria and Wojciech Nowakowski's systems. All the devices presented in their books were built by them and worked almost from the first switching on.
  • #17
    pawlik118
    Level 31  
    prosiak_wej wrote:
    A board made of foamed PVC?

    I do not know, there is info in the description, only that it is a material. Is PVC still an insulator?
  • #18
    ^ToM^
    Level 41  
    acctr wrote:
    żarówka rtęciowa wrote:
    60V 20mA telephone bulb is used to stabilize the amplitude,

    Why this tension? Have you checked its characteristics for voltages equal to the amplitude present in the generator system?


    The bulb is correct because the key parameter is its current, not voltage. Use a light bulb with as little current as possible. Its non-linearity is used for stabilization. This solution was used even in professional constructions.

    Here, Mr. Piotr Górecki described it more easily and I recommend an interesting reading of the PKE episode:

    pke14.pdf Download (1.68 MB)
  • #19
    szeryf3
    Level 27  
    Cool, useful, cheap DIY. Well, and from the goodies.
    I know that the transformer should have thermal protection, but I would put a fuse. Just for my peace of mind. What you will do is up to you to decide.
  • #20
    pikarel
    Level 36  
    The generator is the basis in the electronics studio for testing acoustic devices, and the circuit from the subject has an almost immeasurable value of distortion.

    Foamed PVC is a grateful material for front panels in all DIY; it requires only a knife with a sharp tip for cutting to size and scissors for making holes.
    The switch - is a substitute for what is offered in D-Boxes, i.e. you can disconnect the mass of the system from the ground. A plus from me.

    Now from a different barrel :)
    Who saw a mains fuse in the antenna power supply for the "grid"? - hand up.
    I do not see.
    Who has seen what a damaged transformer 2/XX looks like with the primary winding broken due to overheating?
    Anyone who has seen it knows that no such transformer had a breakdown between the windings, because the windings are not wound on each other, with insulating spacers - but side by side, on a carcass with appropriate insulation (from an injection molding machine).

    I - for example - put on a winter hat and gloves when I open the freezer, because I "believe" that the freezing temperature in it can freeze my ears and hands. Why am I doing this?
    Because the temperature of -20 ° C has frostbite many people's ears and hands, so I prefer to protect myself, and the fact that I look and act like an idiot - it's a little Pikuś.
    :)
  • #21
    pawlik118
    Level 31  
    I saw a damaged Breve 2VA 9A transformer. A break in the primary winding, slightly swollen filler from the bottom.
  • #22
    yogi009
    Level 43  
    żarówka rtęciowa wrote:
    As for the ground switch, I will soon draw and post a diagram.


    That's where I would start the topic. These photos don't say much about the project, and not everyone has an archival RE number on their shelf.
  • #23
    żarówka rtęciowa
    Level 37  
    Hello

    I've attached a diagram to clear your doubts.

    A simple workshop generator m.cz.

    prosiak_wej wrote:
    pawlik118 wrote:
    The front panel is made of plastic - it is non-conductive.

    A board made of foamed PVC?


    It is ordinary ABS plastic.
  • #24
    yogi009
    Level 43  
    żarówka rtęciowa wrote:
    I've attached a diagram to clear your doubts.


    A friend mocks, is the weekend difficult? is this a schematic?
  • #25
    ^ToM^
    Level 41  
    yogi009 wrote:
    żarówka rtęciowa wrote:
    I've attached a diagram to clear your doubts.


    A friend mocks, is the weekend difficult? is this a schematic?


    Why. This is also a diagram, but rather a block diagram.

    Added after 12 [minutes]:

    yogi009 wrote:
    żarówka rtęciowa wrote:
    As for the ground switch, I will soon draw and post a diagram.


    That's where I would start the topic. These photos don't say much about the project, and not everyone has an archival RE number on their shelf.


    Not RE but EP and everyone has access, just go to:

    https://ep.com.pl/archiwum/1995/13113-jan-1995

    Description of the device in the attachment here:
    Generator ...oryjny.pdf Download (1018.42 kB)
  • #26
    yogi009
    Level 43  
    So just paste the link. Looking at the application itself, however, I would opt for the ICL8038 (or its newer variants). Three waveforms, larger range, little layout complication. And five adjustments (even offset).
  • #27
    Gismot
    Level 18  
    CosteC wrote:
    pawlik118 wrote:
    From what I remember, the fuse at the transformers, up to ~2.5VA, is not required. Perhaps this is due to the fact that the very thin wire of the primary winding is not able to carry the current that would give off power that could burn the insulation between the primary and secondary sides.
    e.g. Breve on their products

    I don't know such a recipe... It would be very strange, besides it assumes that there will be no magical failure anywhere else in the device that could lead to a fire..
    The fuse has two roles - protection against fire and protection against electric shock, of which it protects against electric shock only in specific cases - because depending on the position of the plug, the fuse can be on the neutral line.


    As a curiosity, I will add in the factory equipment of Polish production (metal housing) with 10VA transformers, the mains fuse on the primary side of the transformer was not always used either. The secondary windings of the transformer were always protected by fuses. E.g. tuner ELTRA T8010, T 3015, ZRK T7010, EQ DIORA FS 042.

    However, the V40.28 power supply in the Meratronik V640 multimeter does not have any fuse. (very often the transformer is damaged in them)

    In the case of devices in wooden or plastic housings (table radios), the transformer always had a fuse on the primary and secondary sides.

    Modern antenna power supply for continuous operation, which does not have any fuses.
    A simple workshop generator m.cz. A simple workshop generator m.cz.
  • #28
    yogi009
    Level 43  
    Well, the function of the fuse was taken by the transformer. Such goovniane communist material savings in the face of Western economic sanctions.
  • #29
    dipol
    Level 34  
    I scrapped such a miracle when I started working at ZURiT in 1970. To make it easier to service the equipment, a multivibrator was added (to "sow" from early / early / mid-term) on germanium transistors. I had mastered the generators, because in the 4th grade of the technical school I had a shortwave transmitter made on 50 W lamps - for testing the mcz modulator of the transmitter.
    Me, a young goldfinch after a technical school, "old masters" stopped covering with caps so that "young" would not peep - and "borrow a generator" appeared.
    For them, transistors were the realm of SF. A helpful toy - I repaired over 200 radios a month. History has come full circle and has been rediscovered.
    I salute the young geeks.
    The lack of a fuse rather indicates a lack of elementary knowledge of health and safety.
    To protect myself from the "hot" mass, I still have a 500W safety transformer in my workshop from which I power the workbench. In this power supply there is a polymer fuse wound with the transformer winding.
    73!
  • #30
    Mateusz_konstruktor
    Level 33  
    @dipole
    Which bulbs are suitable and which should be avoided?
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