I do not have great experience in high frequency PCB design, thus, i made some design mistakes on the PCB, but i discovered it later on, during the test runs. This is the first PCB design for the circuit:
A slight modification: As i plan to install this project on my workbench, near the main power supply, i have removed the 7805 and 7905 chips. Instead, i get directly the +- 5 volts from my power supply. As for the IC2, you may notice that is missing from the schematic diagram. The PCB was created with the IC2 (TL72P) to control the frequency select and fine tuning. But during the tests, i got bad results, and therefore i replaced it with two 10K resistors. The schematic diagram that follows, corresponds 100% to the PCB that i published above, yet i discourage you to use it for your own projects. Unfortunately, i have not yet design a PCB that has this change corrected.
I tried to have the grounding layer all around every wiring. Also, there is no bridge for the grounding layer, not that this is important. It is all in one piece. Yet, i do have 4 bridges for other positions of the PCB. The fact that i designed this circuit on a single side board was probably a mistake. I will get some more knowledge for high frequency PCB design and re-design this PCB, maybe on a double-side PCB.
The soldering of the parts had to be done very carefully, as the grounding layer had just .1'' insulation. I used the smallest tip i had for my Antex. Here is the PCB with the parts soldered:
The range selector
The range selector is a 12-position single pole rotary switch. Each switch position corresponds to a different capacitor. So, either i would solder the capacitors to the PCB and draw 12 (+1 for common) wires to the selector, or i would do this:
First, i made a ring with a thick single core wire (2.5 mm2). The diameter was about 10mm larger than the diameter of the rotary switch. I cut and soldered the two edges of this wire to make a closed ring. Then, i soldered one terminal of a capacitor to one position of the rotary switch. The other terminal of the capacitor was free, outside the switch's diameter. On this terminal, i soldered the ring. Then, on the symmetrical pin of the switch, i soldered likewise another capacitor. I did this for all 12 capacitors. When i finished, i had all 12 capacitors connected directly on the selector switch, and only 2 wires would now be required to departure from the PCB, the 0V wire which is connected on the ring, and the COSC input for the chip.
I made a ring with a single core thick wire, with diameter roughly 10mm bigger than the switch's diameter.
I cut and soldered the wire to make a closed ring
I soldered one terminal of a capacitor to one terminal of the switch
On the other side of this capacitor i soldered the ring
I please need you to design a circuit base on this Multi-Function Chip which can be used to Switch Electromagnet at Adjustable Frequency from 1hz and above.
Please make the circuit simple as I am not trained in Electronics but I can make things out of simplified circuit diagrams.
This is my frst time here so please bear with me.
Is there a way to adapt this circuit device to function as a part of a tig welder? I had electronics in high school the late 70's and am terribly rusty. I am now more of a gear head and would like to combine the best of two worlds.
@Marc Bonnier i discourage you to use this PCB because it causes a lot of interferences above some MHz. I am not sure if i have any of these PCB files any more (i had a fatal crash some time ago and lost almost all my older project files)
I have a MAX038 chip and I'm planning to make the function generator detailed here. However, I'm having trouble locating the OP37Z op-amp. Do you know where I may be able to find one or can you recommend a replacement?
Hello Jogie. The chip is not produced any more, and is very expensive. I discourage you to copy this circuit. I did this because i had this in stock a lot time ago. If you find it somewhere in stock, it will cost a lot of money. I do not know a replacement part, and i do not think that exists one. But i do know that there are other chips with the same functionality.
Thanks for this site. I now found a fully working function generator, but sir, the chip which u use there is not available in Philippines. Can u recommend another IC to be used that is compatible with your circuit diagram. A replacement for the expensive IC sir coz i cant afford it, our school requires us to make function generator..
Can u send me sir the schematic diagram with their respective components???
The only problem with this project is the chip availability and price. The MAX038 was discontinued by Maxim years ago and one can find it only overpriced on Ebay. Unfortunately there are no direct substitutes and no other chips that go up to 20 MHz as the MAX038 did. The only similar chips around are the XR2206 and the ICL8038 (which has absolutely nothing in common with the MAX038 despite the somewhat similar numeration), both are 20+ years old and both won't go much further one or two MHz.
Nowadays if you want to build a modern signal generator DDS is the solution. Unfortunately it requires an additional MCU, more components and writing code.
I am Anthony Merenda radioamatore with it initials I8CQ, and I am enrolled to grix site Italian web, of electronic amatoriale. And having an integrated maxim 038, I have looked for on the web to find a project and the motor of search google you/he/she has brought me on his/her sito.Visto the project and his/her validity, I ask her if it authorizes me to pubbbicarlo on site web of grix.it. naturally you/he/she will be quoted both his/her site and the planner. aspect his/her news thanks.
antonio snack I8CQ.
P.S. I want to complimenti