Building an ESR meter, some help and someone to check my PCB layout
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Re: Building an ESR meter, some help and someone to check my PCB layout
I think your layout looks good, just, don't trust me, I overlook things sometimes
BTW, what are the dimensions of the board? It looks a little cramped. What are the maximum allowable dimensions of the board for your meter? I can also give a go at designing a board layout too.Muh-soggy-kneeComment
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Re: Building an ESR meter, some help and someone to check my PCB layout
Hmmm..
Some notes:
You leave a lot of empty space under the 7805 regulator. As you only draw a few mA, it won't heat up that much even with 9v input, so you could move the resistors under it. It's unlikely they'll heat from the 7805 enough to change their resistance significantly.
Otherwise, those resistors seem like ideal to be replaced with a bussed resistor array:
http://www.digikey.com/product-detai...1LF-ND/1089000
It's cheap (not including the shipping from Digikey) and saves you board space, it's SIP, it's spaced at 0.1" (2.54mm) so they can go almost parallel near the 16pin DIP.
Moving the resistors towards the top may allow you to turn the 16pin dip chip 90 degrees taking advantage of the empty space under LSP2 hole.
The new space you have above the R17 and C6 would give you some room to distance those pads a bit so that you'd have room for solder mask and to have nice round copper pads for each hole, without two holes getting their round surface mixed together.Comment
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Re: Building an ESR meter, some help and someone to check my PCB layout
Using SMD would help with the space too, it isn't THAT hard to solder 1206 resistors, that is the size that I use.
Edit-0: A better chip would be the 74HC7540. It is an octal inverting schmitt-trigger buffer chip; the inputs are on one side, and the outputs are on the other. Together with marishum's idea of a SIP resistor pack, you can save a decent amount of space! I think you could use the two extra inverting-schmitt buffers in the circuit without any decrease in performance also.
Edit-1: If you go with the chip above, then you can use this resistor array. (It is from mouser though, I am sure that there will be something similar on Digikey too)
Edit-2: You could also use an LM78L05 (5v 100mA) regulator, instead of the large LM7805 one.Muh-soggy-kneeComment
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Re: Building an ESR meter, some help and someone to check my PCB layout
I have thought about using SMD because I would like to practice soldering them. I am going by a previous design and using what is available to me atm because I am trying to fix a Magnavox 50MF231D/37 that has problems. I plan on going through the board cap by cap and an ESR meter would save me considerable time and offer an alternative to just pulling and measuring capacitance or testing for short.
I did see mini 74HC14M in this surplus store and do have a local distributor for SMD components so I may opt for being able to put it in a smaller case at a later time. As for right now, the meter and the box will fit this with a little room to spare fitting it sideways on one end leaving room for the 9v and the back of the meter.
I have been trying to print out the board on my printer but unless I print black and white, I can not print without resizing the image. Which is driving me crazy. So I have changed it to a png and edited it. Going to try to resize it after lunch and see if I can get it. Having a solid black and white image will mean more toner on the transparency, which means better masking. Sure would be nice if my vinyl cutter was not ruined from being in storage. that would be the easiest method. As soon as I get the board etched I will post some pics of my progress.Comment
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Re: Building an ESR meter, some help and someone to check my PCB layout
Oops, post # 18, that R11 should be 3K3 = 3300 ohms = 3.3K ........Comment
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Re: Building an ESR meter, some help and someone to check my PCB layout
Hi as I said in my previous email ,made some component changes to get more gain out of the amplifier .
Also added a small 14volt bulb in series with the output of the Ic so help to cure the drifting problem, pinched this idea from the first instrument HP made the 200.
Barry WilkinsComment
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Re: Building an ESR meter, some help and someone to check my PCB layout
Hi as I said in my previous email ,made some component changes to get more gain out of the amplifier .
Also added a small 14volt bulb in series with the output of the Ic so help to cure the drifting problem, pinched this idea from the first instrument HP made the 200.
Barry Wilkins
Also, did you mean post, not email?
My computer actually just died, so I can't post any schematics or pcb layouts (I am typing this from my kindle fire)Muh-soggy-kneeComment
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