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Author Topic: Again Velleman K7200 0-30V 0-10A Mini PCB Tested  (Read 3361 times)
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gevv
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« on: August 18, 2020, 10:19:49 10:19 »

Hi,

I tried the circuit works fine, sprint layout source pcb drawings and gerber files.

https://youtu.be/6wTsgXGJ5CY


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« Reply #1 on: August 18, 2020, 10:39:43 10:39 »

Only comment to add 'why use sockets for the ic's ?
with todays de-soldering tools, if a damaged ic needs replacing it only takes a short time.

The reason I say this I just had a 40odd year old Analog to Digital card on my bench.
the problem was not with the ic's but both the ic's and sockets had a coating of what looked like carbon
making bad contact and removing the sockets and cleaning the ic legs before soldering them back to the board.
maybe good for another 40 years, but the owner will be long gone.
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« Reply #2 on: August 18, 2020, 10:46:56 10:46 »

Hi,

Yes, you are right. I do not use the integrated socket unnecessarily in the circuits I am sure, but I used the socket in case I tried the circuit for the first time and there were problems in the tests.

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« Reply #3 on: August 21, 2020, 02:54:03 02:54 »

Same here. I used IC sockets when developing/prototyping but not on fully working and tested unit.
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« Reply #4 on: October 17, 2020, 09:47:38 21:47 »

I love this power supply, I brought the bare bones kit from Maplins many many years ago. Had it running for many years. I also did look into making it digitally controlled and changing the displays to an LCD.

After many years service and messing around with, I did look at building another one to make it a dual power supply 0-60V 0-10amp but the cost of the parts I decided not to and brought one.

Now I've seen this it's gave me the bug again to start it all again. The only trouble is the good old LM723N chip is getting harder and harder to find, Lucky for me I found a batch 0f 50 for sale so I brought them  Cheesy.

Now I've been looking at revamping it and making some modifications to it to bring it into the 21St century, Shame they discontinued it.

List of Mods depending on my testing goes.
1. Get rid of the big transformer and switching relay and use an AC/DC converter.
2. Get rid of the parts that make the 18V supply and use a DC/DC converter.  
3. Make it digitally controlled setting the voltage via keypad/Pots by using an 12/16Bit Dac
3A. may consider a rotary encoder or multi-turns pots.
4. Have the power transistor's mounted on the same PCB to bolt straight to the heat sinks that I already have.
5 Make it to channels but only 5amps each rather than 10 as I never used higher than 5 amps really.
6. Have one graphic  display colour   TFT screen.

I've laid out the PCB 100X100mm (get them made in China) with everything the same as the original design just in case my changes I make do not work I can build it has the original spec. Below is a copy of my pcb which I'm just double checking and tidying up to be done. Where the bare copper is I shall add wire and more solder to help carry the current, Track with is 4mm.

Any comments/suggestion's welcome  
« Last Edit: October 17, 2020, 09:51:12 21:51 by Wizpic » Logged

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« Reply #5 on: October 18, 2020, 08:19:55 08:19 »

pickit2

This is a very old design (more then 30 years old), today you design first stage using switching supply followed by linear stage to lower ripple all control by a small micro ,where the switching stage following the linear stage to crate a difference of max 2 volt from input to output in order to reduce power consumption and heating of the power stage.

The use of TH components is probably done due to amateur kit for personal assembly


All the best

Bobi  
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« Reply #6 on: October 18, 2020, 12:32:27 12:32 »

pickit2

This is a very old design (more then 30 years old), today you design first stage using switching supply followed by linear stage to lower ripple all control by a small micro ,where the switching stage following the linear stage to crate a difference of max 2 volt from input to output in order to reduce power consumption and heating of the power stage.

The use of TH components is probably done due to amateur kit for personal assembly


All the best

Bobi  

it is good technique and it will reduce the power consumption also produce less heat then conventional linear power supply i have already design a power supply based on lm2596 as input buck converter and LM338 later replace with LT1086 as it has better line regulation  

sadman
« Last Edit: October 18, 2020, 12:43:25 12:43 by sadman » Logged
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« Reply #7 on: October 20, 2020, 01:27:44 13:27 »

I love this power supply, I brought the bare bones kit from Maplins many many years ago. Had it running for many years. I also did look into making it digitally controlled and changing the displays to an LCD.

After many years service and messing around with, I did look at building another one to make it a dual power supply 0-60V 0-10amp but the cost of the parts I decided not to and brought one.

Now I've seen this it's gave me the bug again to start it all again. The only trouble is the good old LM723N chip is getting harder and harder to find, Lucky for me I found a batch 0f 50 for sale so I brought them  Cheesy.

Now I've been looking at revamping it and making some modifications to it to bring it into the 21St century, Shame they discontinued it.

List of Mods depending on my testing goes.
1. Get rid of the big transformer and switching relay and use an AC/DC converter.
2. Get rid of the parts that make the 18V supply and use a DC/DC converter.  
3. Make it digitally controlled setting the voltage via keypad/Pots by using an 12/16Bit Dac
3A. may consider a rotary encoder or multi-turns pots.
4. Have the power transistor's mounted on the same PCB to bolt straight to the heat sinks that I already have.
5 Make it to channels but only 5amps each rather than 10 as I never used higher than 5 amps really.
6. Have one graphic  display colour   TFT screen.

I've laid out the PCB 100X100mm (get them made in China) with everything the same as the original design just in case my changes I make do not work I can build it has the original spec. Below is a copy of my pcb which I'm just double checking and tidying up to be done. Where the bare copper is I shall add wire and more solder to help carry the current, Track with is 4mm.

Any comments/suggestion's welcome  

Wizpic look at this page

Detail
https://www.electronics-lab.com/elbsupply-linear-bench-power-supply-constant-current-voltage-modes/        

Code and PCB files

https://github.com/knightshrub/elbsupply

another nice design
https://www.instructables.com/Digital-Battery-Operated-Powersupply/
« Last Edit: October 20, 2020, 01:36:15 13:36 by sadman » Logged
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« Reply #8 on: October 20, 2020, 06:27:05 18:27 »


They look interesting and easy to build will have to have a good look through them, put I do love the k7200 PSU design, I know some might say why re-invent the wheel but electronics is all about the fun in designing and a chalange.

When I get round to it if it works Iíll post the results in a new topic, has I donít want to hi-jack this thread as itís a nice pcb laid out from a trusty old design

Wizpic
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« Reply #9 on: October 24, 2020, 05:17:43 05:17 »

Hi,

See the following circuits for the pre-regulator.
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« Reply #10 on: October 26, 2020, 03:41:16 03:41 »

Hi Wizpic in polish magazine a digital controlled power supply publish using LM723 and atmega8 as digital controller for volt and current it will give an idea how to implement digital control to LM723 complete detail uploaded for you. 

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« Reply #11 on: October 26, 2020, 06:16:21 18:16 »


Those power supply designed by amateurs and student with no background in power supply design and are probably bad behave from the noise(ripple out put) or current pulse response point of view and can't be compare to the velleman kit although the velleman kit is an old design type who use the 723 IC as base controller.

All the best

Bobi

 
  
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« Reply #12 on: February 16, 2021, 06:37:52 18:37 »

IMHO, the Precision Power Supply by Elektor (Dec. 1982) is by far the best DIY power supply ever.

It even has the sense inputs so that long cables do not contribute in voltage drop at the end point.
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« Reply #13 on: February 16, 2021, 07:20:51 19:20 »

IMHO, the Precision Power Supply by Elektor (Dec. 1982) is by far the best DIY power supply ever.

It even has the sense inputs so that long cables do not contribute in voltage drop at the end point.

I did a search on this one and Iíd seen that it had some issues with the design not sure if they where ever rectified. I like this k7200 design which I know is just as old but very good and reliable, Iíve nearly completed my front end controller for this (2 channels) works really well Iím just waiting for a couple of parts so that I can check the footprint on them then Iíll send the files off to get the pcbís  made, this can be made to control any psu that uses a voltage to control the outputs
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« Reply #14 on: February 17, 2021, 03:03:39 15:03 »

IMHO, the Precision Power Supply by Elektor (Dec. 1982) is by far the best DIY power supply ever.

It even has the sense inputs so that long cables do not contribute in voltage drop at the end point.

A valid point but I think it need kind of a refurbish.Some components more up to date.But keep the 723. I post the paper here. What

do you(the forum that is)think
Edit I have not taken a deep look into the circuit Smiley But feel free to do so
Edit 2.Sorry for the bad copy. But I had to reduce the size in order to post
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