EEVBlog #930 - Mailbag

[EEVblog]

More Mailbag



SPOILERS:
Dave's first multimeter hack!
Sinclair PDM35 Multimeter
Russian analog multimeter
Canyse 801 data logger
http://electronics-development.eu/
Kickstarter Masso CNC Controller
https://www.kickstarter.com/projects/hindtechnology/masso-the-all-in-one-cnc-controller
http://www.hindtechnology.com/
Lumintop Prince 1000 lumens flashlight torch
http://amzn.to/2dmWXTl
Lumintop micro USB rechargeable 18650 cell teardown
http://amzn.to/2dFCjsQ
Canon Ion Still Video Camera and the VF-50 2" floppy disk

[n3vti]

Sagan is so adorable. 

I have a few extra old RadioShack Multimeters, maybe Dave wouldn't mind a teardown for a future mailbag? Today just so happens to be my birthday and I really want to get rid of most of these meters so I can get the BM235.

Oh, speaking of RS, apparently they're bringing the Tandy name back, in the form of wireless keyboards and mice. I'll post a picture in General Chat.

[psidragon]

So there are 208 pins on that package for the CNC controller, if that helps with the identification. What does the crystal package say? I couldn't get it off the video.

[Vgkid]

That was a nice mailbag.Never thought about multimeters not being fused.

[Chipguy]

The housing of that data logger seems to be from the german manufacturer Bopla:
https://www.bopla.de/de/gehaeusetechnik/product/bos-streamline.html

The stand though is definetly from german manufacturer OKW:
https://www.okw.com/de/Datec-Mobil-Box/A9250909.htm

Cheers

[GUMY]

Chipguy, You are absolutely right. 

[lemming]

So there are 208 pins on that package for the CNC controller, if that helps with the identification. What does the crystal package say? I couldn't get it off the video.

Appears to be 12MHz, I had a quick look on DigiKey and there were some 208 pin Renesas parts, but the location of the two crystals didn't match.

It also appears there's a DAC for the VGA in the lower left corner, and a 64Mbit DRAM to the upper left of the main IC.

[bktemp]

My guess would be a Renesas or Freescale (NXP) controller. Maybe MAC57Dxxx?
http://www.nxp.com/products/microcontrollers-and-processors/arm-processors/mac57dxxx/ultra-reliable-multi-core-arm-based-mcu-for-clusters-and-display-management:MAC57D5xx
They have a buildin videocontroller + GPU, SDRAM controller, stepper motor controllers and QFP208 package.

[G7PSK]

I had a sinclair multi-meter in the early 1980's absolute piece of crap. I dont know how many models they made but the one I had had a frequency range as well which is why I got it. It blew up when I tried to check the frequency of a genset. When I took it apart the case was a re-purposed calculator shell complete with all the holes for the buttons under a sticky cover. After that experience (the meter was in my hand) I never got another digital meter until a few years ago when I started watching the EEVblog up to then I stuck with AVO meters for voltage etc and and tachometers to measure the rpm of gen sets.

[ckambiselis]

About the Lumentop USB rechargeable battery, they probably made it fit by removing/shortening the typical end cap spring from the flashlight.

[max_torque]

I rekon Daves got about 2 years till Sagan makes him obsolete...........   (then we can do a retro Teardown on him    )

[f4eru]

Concerning the CNC controller, meh....

- optoisolated output : points to people not doing right the EMC/ground routing on motor controllers. You really don't need optos if you do your ground routing correctly. You. don't. need. isolation.
- no power components ? you really must wire each power stage wire for wire on screw posts ? meh. That's really mean design
- ground off chip ? no thanks. incompatible karma.

[Jeff_Birt]

Concerning the CNC controller, meh....

- optoisolated output : points to people not doing right the EMC/ground routing on motor controllers. You really don't need optos if you do your ground routing correctly. You. don't. need. isolation.
- no power components ? you really must wire each power stage wire for wire on screw posts ? meh. That's really mean design
- ground off chip ? no thanks. incompatible karma.

You don't 'have' to isolate I/O but it saves you a lot of grief and blowing up your controls when things go wrong. want your 5V (or 3.3V) logic circuits directly connected to your 48V or 80V motor drives? Go for it.

[nctnico]

In many cases the optocouplers are connected to the same ground so they don't isolate anything. Series resistors and zeners are just as good for keeping nasty stuff out of logic circuits and you can't wreck the LEDs in the optocouplers.

[Jeff_Birt]

???If all of the control sides of the optos are share a common ground that is just fine, as well if all the outside world optos share a common ground that is fine (as far as the control is concerned.) If both sides of the optos share a common ground that is far less ideal.

I suppose you think the guys who came up with Ethernet got it all wrong by transformer coupling both ends of the connection?

If you had ever worked in a factory environment with sources of interference everywhere, or if you realize that beginners are going to be wiring up these DIY CNC products, you would not doubt the value if isolation.

[Kleinstein]

Having opto-couplers in a CNC control is a good idea. You may not need it with all inputs / output - especially something like switches are easier without. But there might still be the option to use a bridge instead. It looks like motor control is via RS232 or similar - makes some sense, but I don't know if this is a common standard. At least wiring is not that bad. However normal RS232 would not include isolation.

[NottheDan]

When I took it apart the case was a re-purposed calculator shell complete with all the holes for the buttons under a sticky cover.

Ayup. Look closely at the model in the video. Calculator shell with a custom face plate. I guess in your model they found a way on saving even more on the face plate.

[nctnico]

???If all of the control sides of the optos are share a common ground that is just fine, as well if all the outside world optos share a common ground that is fine (as far as the control is concerned.) If both sides of the optos share a common ground that is far less ideal.

And yet that is what you see on some less clever designs. After all: there has to be some power source to drive current through the LEDs and it does take some thinking that this power source has to be isolated from the rest in order to make a difference.

[reinhardz]

Hi Dave

Thanks a lot for your always interesting episodes. It would be very nice if you made a scan of the schematic of Sinclair PDM 35 multimeter. Many thanks in advance.

Best regards

reinhardz

[EEVblog]

I rekon Daves got about 2 years till Sagan makes him obsolete

I hope so, retirement sound good to me.

[meeko]

The school my Dad taught at had a Canon Xapshot, which was a similar still video camera, using the same video floppy disks, but only did composite video.  I guess it was the predecessor of the Ion?

They used it with a digitizer (Digiview, or something like that?) that connected to the parallel port of a Commodore Amiga.  The digitizer was intended to be used with a B&W security camera, doing a 3 pass capture through red, green & blue filters.  Dad's school used the Xapshot, though, and an electronic colour splitter to separate the red, green & blue channels.

It was pretty neat for the day, but really crusty compared to modern digital cameras.  It would have been at most 640x400, probably only 320x200.  I think it might have used the Amiga's HAM mode, though, to (kind of) do 4096 colours.

[gnavigator1007]

I'm wondering if the note for the CNC controller password meant that the password is literally the word "blank". Seems suspicious that they underlined it.

[Fungus]

I think I've still got a roll of waxy 'electronics' string somewhere. 

[Fungus]

https://en.wikipedia.org/wiki/Video_Floppy

A Video Floppy can store 25 frames of interlaced PAL or NTSC video, 50 frames of non-interlaced.

I've never actually heard of them before.

[SeanB]

I think I've still got a roll of waxy 'electronics' string somewhere. 

I use it every so often, it is great for sewing heavy material. Don't remember how much I used in wiring looms though, it must have been enough that I have 2 spools of white waxed and one spool of an unwaxed brown nylon, plus a good assortment of sailmakers needles. Even have a few sticks of sealing wax around for the unwaxed ones where you needed to make sure it never came undone from the board or pannel.