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Beginners / Re: RGB circuit help
« Last post by Nitrousoxide on Today at 02:16:38 am »
From what I can see from the illegible diagram (please use a proper CAD/CAE program), the circuit will not work.

My next complication would be to add some kind of momentary switch to be able to change the colour to a different selectable colour.
This should not be additive i.e. LED could be Red+Blue(pink) and then switch to Red+Green(yellow) not to white.

I would like this to be made of all discrete components - no microcontrollers!

If you want to cycle between colours, you will need some form of a state machine. This can be achieved through the use of flip-flops (or binary counters) and discrete logic.
For example, you would need 7 states to cover all possible combinations (R, G, B, R+G, R+B, G+B, R+G+B).

Do you have any experience in logic design?

Clearly, after the logic stage there will be a power stage, this may simply consist of resistors and NPN BJT's.
A server rack is likely going to dissipate a few hundred Watts, that is orders of magnitude more than you can reasonably hope to carry away with a Peltier.
No, you can't cool a server rack with peltiers.
Open Source Hardware / Re: Nixie Tap - an ESP8266 Nixie clock
« Last post by Rolo on Today at 02:11:41 am »
Looking at the schematic I see you use a RTC chip in this design. I'm curious if you thought/tryed to make the clock work without this RTC. Having WiFi and NTP sync should work, or did you want the clock still working when "stand alone" ?

Repair / Heil HM-10 Dual repair
« Last post by innkeeper on Today at 02:11:28 am »
I got my hands on a Heil HM-10 Dual element microphone at a hamfest that in pretty sad shape but salvageable.

If anyone can take a picture of a Heil HM-10 Dual microphone elements and how they are mounted, that be great!

The microphone elements broke loose from the mount at some point and it seems someone thought the solution for that was duct tape... which has now become all gooey. What a mess.  it is otherwise coated with a thick layer of nicotine stains, in the pic below, the ring on the top of the mic is supposed to be silver and not gold looking and the lettering should be white. Though I think this can all be cleaned up.

its also missing the screw that held the mic into the body. you can see where someone had put tape along the base of the mic, where they held a wrong sized screw in place to keep the mic jack in the mic body.  the previous owner loved tape I guess :P 

wiring all seems ok. it doesn't look like anyone has messed with the insides.

the elements look like they might have been epoxied to the top of the plastic mount but, I've seen pictures of the inside of an HM-5 where the elements had a holder and were mounted vertically. I don't think this is the case for this one as there simply isn't enough room for that.

General Chat / Re: FIFA World CUP 2018 - Who will win?
« Last post by Bud on Today at 02:09:03 am »
The referee did not do anything extaordinary awarding the penalty. I watched the most if not all of the matches and penalties were given for much less than this one.
Repair / Re: When thread lock runs out at factory...
« Last post by james_s on Today at 02:06:36 am »
I would have been tempted to just say "Sure, if you say so" and just make sure it was known who made the decision to substitute those transistors when the whole production run fails.
Beginners / Re: design simple amp
« Last post by LvW on Today at 02:03:37 am »
Without any external load - and assuming that all capacitors are large enough for coupling the 1kHz - the actual gain is Av=-6k/25=-240.
Because I do not see that the load is specified, the remaining task is to find the proper load resistor for reducing the gain to -200.
That is a simple task.
In case, the load is given the effective gain determining resistor is 6k||10k=3.75 kohms and the gain can never reach the value of -200.
(Av=-3.75k/25=-150) .
Comment: Modifying the base resistors cannot help at all !
Hi :-) I've been a member here longer than I've been at SiFive. I'm not a founder or manager or spokesperson or anything like that, just a pleb programmer. All opinions are most definitely my own. I liked the tech and its possibilities so much I joined the company.

The business model is, I would say, something like RedHat. Nothing stops you putting together your own Linux distro or using one of the many free ones, but some people prefer to pay money for a supported version, with components and versions of components that have been tested and certified to work together.

Hello! :D

One difference I see between RedHat and SiFive is that SiFive has a silicon foundry in between their team and the delivered products, and once they hit volume, this is presumably a significant portion of the per-unit cost. It feels like there is an opportunity for SiFive to get undercut by second sources of their own products, whether from a different foundry, or by another foundry customer with better foundry relations. OTOH, if you are literally distributing binary copies of a RedHat image, this is still illegal as far as I know. I realise people thought of this before starting a multimillion company, I'm just curious!

AMBA has a free license but it's not unlicensed. You have to agree to the license terms, and it seems possible ARM could decide to withdraw a license.

There is particular confusion around whether you can use AMBA with non-ARM CPU cores. Some people interpret the wording to mean you can't have a non-ARM CPU in your AMBA system. Others interpret it to mean if your core executes ARM instructions then it must have a paid-for license from ARM.

None of which has I think been tested in court.

Oops. I should have looked into that more deeply when I started working on my AHB-lite RV32IMC core...  :'( that does put things in context though. And I guess hobby projects are mostly safe.

Using AMBA in a RISC-V system might be low risk, but could still be the largest risk of getting sued.

SiFive uses Berkeley's "TileLink" point to point interface. I think it's roughly equivalent to AXI4 ACE. We have high performance adaptors to AXI if you need them.

I think some others are using WishBone? I'm not aware of anyone rolling their own from scratch.

Oops, yeah, TileLink is the one I was thinking of. The one that's in RocketChip too right? I guess my brain went "also berkeley + also new/in dev -> same team".

I wasn't aware you could do high frequency * area product (i.e. insert pipe stages without throughput reduction) and coherent stuff with Wishbone, guess I should look into that more! I have only seen it used in a similar context to APB.

Given the ubiquity of AMBA slave IP (in my corner of the industry at least), I still feel like it won't be too long until we get that ARM/AMBA test case in court :D will be interesting to see how that is handled. And also whether there is a line drawn between AMBA busfabric vs non-proprietary busfabric and adapter to AMBA slave, since the adapter + slave effectively combine to make a non-AMBA slave. As you said though, the validity of the case doesn't really matter.

I need to understand AMBA licensing better, thank you for the pointer
Crystal is an activated rosin flux, with the different grades having different levels of halides. Halides are additives used to make brighter joints on oxidized metal surfaces: if you are soldering to new bright tin parts and new boards, you can use halide-free fluxes, while some halides make rework easier on old assemblies with oxidation or corrosion. Crystal 511 has 1.1% halides, Crystal 502 has 0.2%, and Crystal 400 has 0%. These would all be considered RMA fluxes (rosin, mildly activated), which don't necessarily need cleaning unless your process requires it.

362, 366, 311, and x39 are also activated rosin fluxes, which would be considered RMA or no-clean. They have various levels of activators, as described in the datasheets, for different application requirements.

The above would all be suitable for normal hand soldering and rework.

Hydro-X is water soluble ("organic") flux and should not be used unless you have extensive capabilities for cleaning and testing. The data sheet says that soldered assemblies need to be destructively tested for ionic contamination and the wash water conductivity monitored :palm: It seems to be made of citric acid in a glycerol and PEG carrier.
Arax is an acid flux, made of ammonium chloride and ammonium fluoride in a urea buffer. Like all acid fluxes it is unsuitable for electronics.

These ones would not be recommended.

Thank you! They didn't have 362, so I'll see if they have 311 and I'll go with that or Crystal 511.

I also agree that for a hobbyist, it is best to use a no-clean flux.

A washable flux, if washed incorrectly, can cause long term reliability issues.

Some people have reported that they have washed boards using  warm water with mild soap, scrubbing them with a clean toothbrush, and rinsing them in de-ionized water.
The caveat I see here is the different tap water qualities around the world. Some locations have very hard water which could leave residues. Also some soaps, which are mostly intended for human use, have lotions and moisturizers. Again, it depends where in the world you get that soap, as formulations will vary.

Therefore, stick with a no-clean flux.

I see, it's nice to know that!
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