Another Horn Question-74 Cj5

It's not 15. This is 15 and 30 in my hand.



Looks more like 50 to me.

Parts order looks fine. I would point out one thing, then the rest is for your edification, not criticism. You need to use 3 of those capacitors on the input. They are each 100nF (0.1uF) and the data sheet calls for 330nF of bypass on the input. I would tie them together before I mounted on the chip.

Something like this, but with your capacitors.



RDER71H334K1P1H03B would be better on both the input and output. Increasing the capacitance values from the data sheet would be fine. You could go to 470nF or 1uF and it would work perfectly. The manufacturers optimize those values so their recommendations are the most economical possible. This matters to a manufactured product that will use thousands of these parts, but not to you.

More about solder: The Kester 1lb roll that I listed above would probably last for the rest of your life. I do a lot more soldering than you do, and a 1lb roll lasts a decade or more. The solder you bought is fine, though the Kester might make your work a little easier. I'm sure the alloy they printed on the package is correct, 60% tin and 40% lead. The ideal ratio is called the "eutectic alloy" and has the lowest melting temperature for tin/lead at 63/37. It's only a few degrees lower than 60/40, and 60/40 has a place in the vernacular somehow. However, if that solder falls down it will be due to the flux. Kester is the brand, and they use the best flux in the right proportion. Melts easy, wets nice, not a lot of fumes.

https://www.amazon.com/Kester-24-63...0068IJOU/ref=psdc_13837421_t1_B00068IJPO?th=1

Another reason to buy a 1lb roll: it contains lead. Manufacturers use lead-free solder now because the components could be recycled at some point, and lead has obvious issues. I'd guess there are locales where products made with tin-lead solder cannot be sold. Lead-free solder is universal in plumbing now. Consumers in the USA are free to buy tin-lead electronics solder, but not for plumbing. Use in DIY electronics could be banned too, or lack of demand may force it off the market. Tin-lead flows nice, melts easily and makes shiny joint. Lead-free is an option, if your personal exposure is important to you.

Regarding the components, the fewest I would buy of any of these small, inexpensive passives is ten. It's good to have extras, because you might want them for other projects, and you want the freedom to clip them out and start over, rather than trying to unsolder and reuse. Or you could pass them on to someone else who wants to do this project. Looking at prices, you bought 4 resistors at 48c, with 10 costing 61c. You bought 6 capacitors at $1.86, with 10 costing $1.51. Quantity discount for these small generic parts is substantial.

Ceramic capacitors work well for bypass, as in this application. However, they are not very linear compared to plastic film capacitors, and this causes distortion if placed in the signal path. For this application, it does not matter, though I would consider upgrading the caps to a film type. The left-overs in my junk box could then be used for other things.

For anyone doing projects like this with very little to spend, Digikey has a program for you. If you send them your order by mail in an envelope, with a check, they will fill your order and cover the shipping - no additional charge.

 

Tim, Thankyou so much for helping me with this . I have made some changes to my parts order with a minimum of 10 each of the parts and changed the caps to the .47uf with longer leads. The caps are also film type rather than ceramic. I will order with Mouser, it looks like DigiKey is out of stock on the resistors. Below is my new order, please review an let me know if I should make any changes. I apologize for dragging this on so long, but I appreciate your help I would have never gotten it done without your expert knowledge. Jim



Description
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1

Mouser #:
511-L7805CV
Mfr. #:
L7805CV
Mfr.:
STMicroelectronics
Customer #:

Linear Voltage Regulators 5.0V 1.0A Positive
RoHS Compliant
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10
$0.444
$4.44

2

Mouser #:
603-MFR-25FTE52-47R
Mfr. #:
MFR-25FTE52-47R
Mfr.:
Yageo
Customer #:

Metal Film Resistors - Through Hole 47 OHM 1/4W 1%
RoHS Compliant
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10
$0.061
$0.61

3

Mouser #:
598-474MSR250K
Mfr. #:
474MSR250K
Mfr.:
Cornell Dubilier
Customer #:

Film Capacitors 0.47uF 250V 10%
RoHS Compliant
QuickView

 

Hi Jim -

I presume you are going to use the resistors for testing your gauges, not including in the CVR circuit. There is no need for a resistor in the replacement CVR.

If Digikey does not have those resistors from Yaego, likely they have them from Xicon. Or look at carbon film or carbon comp types instead of metal film. Use their search tool, select passives, resistors, and look for 1/4W or 1/2W 47 ohm parts in an axial package, then sort the results by price. Select in-stock too. You should find something within a few cents of the Yaego parts.

The multilayer ceramic capacitors are fine for this application. You will see no advantage changing to a film capacitor for this application. You also won't see any advantage in increasing the capacitance value. A few times more capacitance won't hurt, but it won't make a detectable improvement. Two of the RDER71H334K1P1H03B or of the RDER71H474K1P1H03B will work just the same as hundreds of other acceptable parts.

I used the brown Panasonic caps in my other thread because I had them, and because they would work. I have a few ceramic caps in my junk box, but nothing like those values. The values were picked not because they were better, but because they are above the minimum requirement.

Maybe I should not have brought up the issue about film caps. Let me chat some about capacitors.

Your basic capacitor has two conductive metal plates with some insulation between, the "dielectric." This can be air, paper, plastic, ceramic, glass, mica, etc.

The multilayer ceramic caps have an advantage in this application - the package size is small. They are also cheap and tough. You could use a plastic film cap instead, but there would be no detectable difference in performance.

Plastic film caps are made using a thin plastic film of various types as the dielectric. The cheapest is polyester (mylar), with other possible plastics, some familiar such as polypropylene and teflon, and some less familiar like polyethylene terephthalate (PET). The plastic dielectric is chosen for its physical characteristics. There is also construction to consider, including lead orientation (radial or axial) and whether the part uses foil of various different metals between the layers of dielectric, or is metallized. The most common and least expensive film cap is metallized polyester, where (aluminum?) metal vapor is deposited on one side of the plastic film and serves as the plate.

You can increase the voltage rating of a capacitor over the specification. No problem generally, if it will fit. As the voltage rating increases, the plastic film must be thicker. Thinner dielectric will be punched through (arcing) at higher voltages, destroying the cap and maybe the circuit. This thicker material affects 1) cost and 2) size. More material costs more money, and larger parts cost more to make, warehouse and ship. Thicker material increases size in two ways. First, it's simply bulkier for the same area. Second, as the material gets thicker, the distance between the plates (the conductors) increases, which reduces the capacitance for a given area of plates, requiring larger plates. High value capacitors at high voltage are big.



Polypropylene (likely) film cap, 10uF at 1000VDC.

Also, for audio, any circuit with aspirations of high fidelity would not use polyester caps. Polypropylene and Teflon are much better, with lower distortion. They are also more expensive.

tl;dr

Those 250V caps aren't doing anything positive for you. Suggest you go back to the 25V or 50V Murata ceramic caps at a higher value; 330nF, or 470nF if you prefer.

 

Tim, Thanks for the post on the capacitors and their construction. It really helps me to understand how they work and why we need them. This has been a really interesting thread for me, as I enjoy learning new things.
I was able to find all the parts I need at Digi-Key including the 47 ohm x 1/2 Watt, 50 Volt, resistors to test my new CVR.
I also got the two ceramic capacitors you recommended. I ordered several extras of each of the parts to share if you or someone else need some. I will post some photos when I build my new CVR. Thanks again, Jim