Author Topic: EEVblog #776 - World's Smallest Digital Dosimeter  (Read 40045 times)

0 Members and 1 Guest are viewing this topic.

Offline SNGLinks

  • Regular Contributor
  • *
  • Posts: 130
  • Country: gb
Re: EEVblog #776 - World's Smallest Digital Dosimeter
« Reply #50 on: August 10, 2015, 11:52:00 pm »
Thanks, I'll get that exact calculator if possible.

Right where I live the soil is basically sand and river sediments but the mountains nearby are mostly made of granite and that's why radiation is higher than average. I hope this device can detect the extra radition.

Besides that, I think that the only potentially highly contaminated area in Spain is near a small southern town where a yankee plane accidentally dropped 4 atomic bombs in 1966 and the explosives in one of them detonated spreading plutonium over a large area. Thankfully it wasn't a nuclear explosion. They cleaned most of the stuff but as far as I know there are places that are still contaminated. I might visit that place one day.

That's near Vera Playa where I go on holiday every year!
 

Offline JackM

  • Regular Contributor
  • *
  • Posts: 63
  • Country: ca
Re: EEVblog #776 - World's Smallest Digital Dosimeter
« Reply #51 on: August 11, 2015, 10:00:37 pm »
Total cost ordering in 1's is about 60€. If anyone is interested I can share a cart for digikey/mouser with everything you need in exact quantity (once you stockpile about 8 large boxes full of leftover SMD's you start seeing the value of ordering just two damn 0603 resitors even if that's more expensive than ordering 25 or 50 as you did when your room had more space)

I am interested in sharing a cart. I am located in Canada however, which might make things more difficult. Let me know!
 

Offline TheElectricChicken

  • Frequent Contributor
  • **
  • Posts: 480
  • Country: au
Re: EEVblog #776 - World's Smallest Digital Dosimeter
« Reply #52 on: August 12, 2015, 12:41:11 pm »
because it need complicated milling like this and this. It make by the hands with Dremel and "file" in first prototype. Last versions fully doing on CNC machine.

I want to help with this important project. I want to make for myself. I can print 3D, I can Draw 3D. I design for 3D printing. Can you post measurements ? I can draw and post STL file for 3D printing for free. I want to help.
 

Offline shodan@micron

  • Regular Contributor
  • *
  • Posts: 145
  • Country: ru
    • My personal page
Re: EEVblog #776 - World's Smallest Digital Dosimeter
« Reply #53 on: August 12, 2015, 03:29:57 pm »
TheElectricChicken - sorry i can't help you.
But dont worry, i product this case many-many hundred pieces and of course in molded high quality plastic.
If I reach an agreement with the milling manufacturer, i share that design.
 

Offline JackM

  • Regular Contributor
  • *
  • Posts: 63
  • Country: ca
Re: EEVblog #776 - World's Smallest Digital Dosimeter
« Reply #54 on: August 12, 2015, 11:33:24 pm »
shodan, I've got a question about the chosen values for the resistor network configuration on the buck converter.

Based on the schematic, you've chosen to go with the 4-resistor configuration detailed in the TPS62736 datasheet. It's basically two resistor voltage dividers for the VOUT_SET and the VIN_OK_SET pins that determine the output voltage and set the acceptable VIN threshold to control the VIN_OK output indicator logic pin.

In the TPS62736 datasheet it recommends that the sum of the two resistors in each divider be 13 Mohm. In your schematic you've got a 7.5 Mohm and a 5.1 Mohm resistor for the VIN_OK_SET divider. I was wondering why you chose the 7.5 Mohm instead of an 8 Mohm resistor? Is it because you wanted a slightly lower (2.989V) VIN_OK threshold? I would have figured you'd go for 3.1V as a threshold, but maybe there is something I'm missing here.

Also, for the resistor divider on the VOUT_SET pin, the sum of the two branches (R16 + R17||R20) is no where close to 13 Mohm, it's more like 5.5 Mohm. Why is this? Is it to achieve a very slightly higher input quiescent current?
 

Offline shodan@micron

  • Regular Contributor
  • *
  • Posts: 145
  • Country: ru
    • My personal page
Re: EEVblog #776 - World's Smallest Digital Dosimeter
« Reply #55 on: August 13, 2015, 04:25:48 am »
JackM, please read datasheet again, on this time read carefully!

13M is not "recommended" value, it is maximum possible value.
Quote
The sum of the resistors is recommended to be no greater than 13 M
It almost has no difference between "1M sum" and "13M sum" (see Figure 22), because that, difference between 5M and 13M is irrelevant.
Also should be noted, 5.5M mode is used only when current is large (illumination, USB, display is active). In this case converter current is irrelevant too.

VIN_OK_SET  - its calculated to 3 volts limits to protected Li-Pol battery. But device work stable only when voltage is higher 3.1-3.2V, this is also valid in my opinion.

Dear Jack, do not worry about current, many times I calculated him and measured with high-precision Agilent 34410A, it is incredibly small.
« Last Edit: August 13, 2015, 10:11:19 am by shodan@micron »
 

Offline dmg

  • Regular Contributor
  • *
  • Posts: 97
Re: EEVblog #776 - World's Smallest Digital Dosimeter
« Reply #56 on: August 14, 2015, 10:31:30 am »
Hi, I have just received the two SBM-10 I ordered. I am concerned because they make a rattling noise when you move them, like they have something loose inside. Is this normal or did I get two broken geiger tubes?
 

Offline Rubi

  • Contributor
  • Posts: 22
  • Country: at
Re: EEVblog #776 - World's Smallest Digital Dosimeter
« Reply #57 on: August 14, 2015, 01:08:17 pm »
Hi

Mine also rattles, hopefully this is by design.

Cheers
Michael
 

Offline shodan@micron

  • Regular Contributor
  • *
  • Posts: 145
  • Country: ru
    • My personal page
Re: EEVblog #776 - World's Smallest Digital Dosimeter
« Reply #58 on: August 14, 2015, 03:25:22 pm »
I have that on sbm-20 sometimes. But on sbm-10 i dont found this symptoms.
Almost every time, sensor with that noise works normal.
 

Offline dmg

  • Regular Contributor
  • *
  • Posts: 97
Re: EEVblog #776 - World's Smallest Digital Dosimeter
« Reply #59 on: August 15, 2015, 04:47:08 pm »
The seller has told me that some SBM-10 were manufactured with fixed getters, while others have unfixed getters and thus they rattle. Is that a possible explanation?

They don't rattle the same way, one of the tubes sounds like if it had a completelly loose ball inside that can move in any direction while the other sounds like it has a ball attached to some flexible structure/spring. I'm not sure about what's the deal in here, I don't know how the internal structure/components of this tubes would look like. On the other hand considering how small they are I find them quite difficult to break...
 

Offline shodan@micron

  • Regular Contributor
  • *
  • Posts: 145
  • Country: ru
    • My personal page
Re: EEVblog #776 - World's Smallest Digital Dosimeter
« Reply #60 on: August 15, 2015, 05:00:49 pm »
Quote
fixed getters

Sorry i don't understand you :(

In any case, this conversation does not make sense. Sensor or good or bad. It is important in this situation.
I unfortunately do not know skills such telekinesis, you should check the sensor in the device.
If it depressurization, it do not work at all. (if sealing glass in sensor is broken)
« Last Edit: August 15, 2015, 05:18:15 pm by shodan@micron »
 

Offline dmg

  • Regular Contributor
  • *
  • Posts: 97
Re: EEVblog #776 - World's Smallest Digital Dosimeter
« Reply #61 on: August 15, 2015, 05:21:21 pm »
I won't get all the parts until late august so I won't be able to test the tubes until then... and ebay buyer protection will have already expired by then, that's why I'm investigating if this rattling is important or not. Apparently rattling SBM-20's are sometimes sensitive to movement and that would be unacceptable for me:
https://mightyohm.com/forum/viewtopic.php?f=15&t=3388

This is exactly what the seller has told me about the fixed/unfixed getters:
Quote
Some manufacturers made tubes with fixed getter, but few manufacturers made is unfixed. it is absolutely normal.

In vacuum tubes (triodes, pentodes, etc) the getter is typically a ring of metal  that they heat after the tube is sealed (they call that flashing) so it sputters a coating of metal that adsorbs residual gases and helps to keep the vacuum. As far as I know geiger tubes aren't in a vacuum and don't require a getter. (https://ru.wikipedia.org/wiki/%D0%93%D0%B5%D1%82%D1%82%D0%B5%D1%80_%28%D0%B3%D0%B0%D0%B7%D0%BE%D0%BF%D0%BE%D0%B3%D0%BB%D0%BE%D1%82%D0%B8%D1%82%D0%B5%D0%BB%D1%8C%29)
 

Offline shodan@micron

  • Regular Contributor
  • *
  • Posts: 145
  • Country: ru
    • My personal page
Re: EEVblog #776 - World's Smallest Digital Dosimeter
« Reply #62 on: August 15, 2015, 05:29:59 pm »
This sensor make only one manufacturer.

As i say, my sbm-10 tube don't have noise. (I soldered more 40 sbm-10 tubes, and 20 tube i get in my store right now)
This tube sealed by glass and special compound.
No "Getter".

Sorry i can't help to you in this. All i know already said.

Now i ask my friends about it. Maybe him know.
Yes, one my friend have one with noise, him tells it work good.
« Last Edit: August 15, 2015, 06:15:12 pm by shodan@micron »
 

Offline dmg

  • Regular Contributor
  • *
  • Posts: 97
Re: EEVblog #776 - World's Smallest Digital Dosimeter
« Reply #63 on: August 25, 2015, 10:46:05 am »
Today I've received the PCB's and cases and everything fits well. The only components I'm still missing are the screens (on their way but quite delayed because of some "chinese military manouvers"), the vibration motors and some diodes that were out of stock and got sent yesterday so they'll arrive tomorrow. I would have assembled the PCB today if I had the missing diodes... I'm travelling tomorrow and I'll be out of town until september so I'll have to wait.

I have 6 spare PCB's. Let me know if anyone wants one.

 

Offline shodan@micron

  • Regular Contributor
  • *
  • Posts: 145
  • Country: ru
    • My personal page
Re: EEVblog #776 - World's Smallest Digital Dosimeter
« Reply #64 on: August 26, 2015, 06:45:03 am »
I started assembling this version too.

But i found error on this PCB :palm:
thermal-barrier on pads is missing some place.
Nevertheless i continue build this PCB.

It is not very bad, but i disappointed  :'( :'( :'(
Now i fix this and reload file to my FTP.

 

Offline Rubi

  • Contributor
  • Posts: 22
  • Country: at
Re: EEVblog #776 - World's Smallest Digital Dosimeter
« Reply #65 on: August 29, 2015, 05:22:01 pm »
Hi

I ordered the 8.06 pcb, does the 8.02 firmware work with this board ?

Is it possible to buy one or two cases from you ?
I am not the best in cutting plastic,...

Cheers
Rubi
 

Offline Rubi

  • Contributor
  • Posts: 22
  • Country: at
Re: EEVblog #776 - World's Smallest Digital Dosimeter
« Reply #66 on: August 29, 2015, 05:23:58 pm »

I have 6 spare PCB's. Let me know if anyone wants one.


I could also give some away within the european region.

Cheers
Rubi
 

Offline shodan@micron

  • Regular Contributor
  • *
  • Posts: 145
  • Country: ru
    • My personal page
Re: EEVblog #776 - World's Smallest Digital Dosimeter
« Reply #67 on: August 29, 2015, 05:57:26 pm »
firmware version 4.02 work on all 4.** PCB
I do not sell case.
 

Offline dmg

  • Regular Contributor
  • *
  • Posts: 97
Re: EEVblog #776 - World's Smallest Digital Dosimeter
« Reply #68 on: August 30, 2015, 07:38:49 am »
What do you mean by thermal barrier is missing in some pads? Does it mean that you wanted pads to connect like the left image and they connect like the right one? [img]http://i.stack.imgur.com/MkZdx.png[\img]

I still haven't received the screens but now at least they have  left china.

BTW I have 6 cases and I only need 2. I don't think I'll get the machining right the first time and I'll sacrifice one for testing the plastic with my cnc's tools to get the correct speed and feedrate. In the best case scenario I'll get 4 machined cases so 2 spares if anyone wants one.
 

Offline shodan@micron

  • Regular Contributor
  • *
  • Posts: 145
  • Country: ru
    • My personal page
Re: EEVblog #776 - World's Smallest Digital Dosimeter
« Reply #69 on: August 30, 2015, 07:51:37 am »
Yes.
It must be as right image. But it rule is missing on some polygons.
« Last Edit: August 30, 2015, 07:58:52 am by shodan@micron »
 

Offline osiixy

  • Contributor
  • Posts: 16
  • Country: 00
Re: EEVblog #776 - World's Smallest Digital Dosimeter
« Reply #70 on: August 30, 2015, 10:06:48 am »
At the first blink it was not obvious what that image tried to show, so probably the info below would be helpful to others also.

thermal relief
Since copper is an efficient heat sink, connections to a large region of copper would be very difficult to solder - the copper heat sink prevents you from adequately heating the connection. To fix this, small cutouts are made around each such connection to create a thermal barrier, so that heat applied to the connection stays at the connection. Such a set of cutouts, and the copper bridges that remain, is called a “thermal”. Thermals come in many patterns, which allows the designer to ensure adequate electrical connectivity and/or manufacturability.


Pins with no connection, three types of thermals, and no thermal.



Thermal pads can be seen in several locations on this Printed circuit board (PCB), in particular, the bottom pad of the three vertical pads in the top left corner.



Sources:
« Last Edit: August 30, 2015, 01:02:23 pm by osiixy »
 

Offline dmg

  • Regular Contributor
  • *
  • Posts: 97
Re: EEVblog #776 - World's Smallest Digital Dosimeter
« Reply #71 on: August 31, 2015, 06:32:21 pm »
Well, I've almost assembled one ultramicron. I still haven't installed the geiger tube because I've run out of isopropyl alcohol so I can't properly clean the PCB yet, I'll buy some tomorrow and install the geiger after cleanup.

Here are some pictures:
Part way through assembly:

After reflow and fixing some minor shorts. Note the flux residue.(yes, I've reflowed the motor but I think these are reflowable and if not... well... YOLO):

Charging the battery (led not visible due to flash):


As you see I've done a little mod to include a connector for the battery. It's an SMD connector hacked to somewhat fit in there. I've checked and there should still be enough clearance with the case. I've also checked that the geiger can still be assembled and fit in the case this way.

I have uploaded the DFU bootloader succesfully and then loaded the firmware via DFU. No problems there. The micron is detected as a virtual com port but I have issues with the USB geiger program. It doesn't detect the micron automatically (I've assigned the micron to COM2) and this is how the program looks like in my computer (Win 7 64bit, windows classic theme, 1920x1080 screen resolution):


Any clue?

Also, after assembly, programming and powe up I've checked the voltage at the tube terminal and my crappy multimeter tells me it's 200V when it should be 400. Probably the multimeter is loading the supply too much to keep the voltage up... what do you think? I'll check with a real high-z meter at work one of these days.

« Last Edit: August 31, 2015, 07:11:12 pm by dmg »
 

Offline shodan@micron

  • Regular Contributor
  • *
  • Posts: 145
  • Country: ru
    • My personal page
Re: EEVblog #776 - World's Smallest Digital Dosimeter
« Reply #72 on: August 31, 2015, 07:17:50 pm »
dmg

After you connect the display you need enter to service menu and check "Pump" menu item, it must be "8T" value for your 4.06 PCB.
Until then, please do not turn on the device! On long time working with incorrect settings RUM mosfets can be damage.

You cannot measured voltage directly with incorect Pump settings. And also you cant measured it on sensor pin directly.
It needs very high input impedance high voltage voltmeter, more 100MegaOhms.

You can measured voltage on HV capacitor leads. With standard multimeter (10M input inpedance on DC volt range) It be more 330V.
But it can be measured with an little error by your 10M voltmeter.

"Reverse" service menu - it sets mirrorring image on display. (to compatible with original and china screens)

Enable service menu - Hold "up" key and powerup device. After it bootup you can see in menu hidden menu items.


About USB... you must check.... STM virtual com-port number in you device manager must be equal USB Gaiger settings.

When device be with screen and all settings is right, you need measured "3V" line. When screen is on, it must be 3.08V... when screen is off avg. 1.9V

Afrer you do it, i tell to you new instructions.


About program windows... hmm i think you use in system big fonts or some else.
I cant see this problem on W7x64.
Try run software in Vista compatible mode or some else compatible settings.
« Last Edit: August 31, 2015, 07:34:56 pm by shodan@micron »
 

Offline dmg

  • Regular Contributor
  • *
  • Posts: 97
Re: EEVblog #776 - World's Smallest Digital Dosimeter
« Reply #73 on: August 31, 2015, 07:33:59 pm »
Ouch, I've turned it off right now, I hope I haven't fried the mosfets. I checked the voltage at the HV cap and my crapmeter says 317 V. Anyway I still have materials to build another one in case this one doesn't work or I've fried something.

I'll have to wait for the screens as I still haven't received them. Hopefully they'll be here this week....

edit: Yes, I run on medium or big fonts. But don't worry, after you dowload the logs it becomes usable.
« Last Edit: August 31, 2015, 07:36:41 pm by dmg »
 

Offline shodan@micron

  • Regular Contributor
  • *
  • Posts: 145
  • Country: ru
    • My personal page
Re: EEVblog #776 - World's Smallest Digital Dosimeter
« Reply #74 on: August 31, 2015, 07:40:16 pm »
Don't worry, i don't see fireworks on wrong settings. :)
The damage is one of the unlikely variants. It need too long time turn on...

« Last Edit: August 31, 2015, 07:42:05 pm by shodan@micron »
 


Share me

Digg  Facebook  SlashDot  Delicious  Technorati  Twitter  Google  Yahoo
Smf