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Author Topic: UT61E Auto Power Off Modification  (Read 26020 times)

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Offline DeanA

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UT61E Auto Power Off Modification
« on: July 16, 2012, 10:09:55 PM »
I have come up with a relatively simple modification to the UT61E which enables the auto power off. Another small modification to the RS232 interface board automagically disables the auto power off when connected to the P.C.

When the RS232 data out function is enabled on the ES515922 by connecting the RS232 pin (pin 111) to V- the auto power off function is disabled. On the UT61E the RS232 output is permanently enabled with a PCB connection from pin111 to V-.
Fortunately the UT61E optical isolation port for the PC interface has a clear window for 2, 3mm LEDs and only the transmit LED is fitted. I added an 3mm NPN IR phototransistor to the spare optical port with the collector connected to the RS232 enable pin (pin 111) and emitter connected to V-.

The RS232 interface board also has a spare window position for a TX LED from the PC. The interface PCB even has a position for the 3mm TX LED connected between V+ and TXD from the PC which is not fitted. I fitted a 3mm IR LED and a 10K current limiting resistor to the interface board. The TXD line from the PC idles low so the IR LED is permanently on when connected to the PC.

So now, when the interface board is slid into the optical port of the UT61E the IR photo transistor added to the UT61E turns on and connects the RS232 enable pin to V-. This enables the RS232 output and disables the auto power off mode of the meter. The PC icon in the bottom left hand corner should turn on when the RS232 optical port is connected to the UT61E with the interface software connected.
The UT61E interface software should be running for everything to work because the RS232 handshaking lines must be in the correct state to power up the RS232 interface board.

More details can be viewed here www.designelectronics.com.au/DesignElectronics_UT61E-APO.htm.

Regards,
Dean


Offline ModemHead

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Re: UT61E Auto Power Off Modification
« Reply #1 on: September 18, 2012, 11:52:05 PM »
Thanks much for posting this information.  Using it I was able to easily modify my UT61E to regain it's APO functionality.

I didn't have a 3mm IR LED, so I used a clear red high-efficiency LED in the RS232 interface module. I used a junkbox photo-transistor in the meter, affixed to the circuit board with some plastic-repair putty.  This keeps from having fiddly little wires connecting the two halves of the case.  It all works nicely.  Data output is enabled immediately when the software turns on the RS-232 handshake lines.

The LCD even has an APO icon, which is now on, and the data-output icon is off. I notice that the APO icon goes off if you hold the yellow button down when turning on the meter.
 

Offline T4P

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Re: UT61E Auto Power Off Modification
« Reply #2 on: September 19, 2012, 01:34:13 AM »
Did you guys use a dremel and attack the interface module or what?  :P
http://the4thpin.comeze.com <-- Rants and Reviews! sorry my english  :palm:
 

Offline ModemHead

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Re: UT61E Auto Power Off Modification
« Reply #3 on: September 19, 2012, 02:53:08 AM »
Did you guys use a dremel and attack the interface module or what?  :P
I scored the seam around the module by repeatedly dragging a hobby (X-acto) knife backwards across all four sides.  When the scores were deep enough, the module came apart easily with just a little persuasion from a spudger. Not a job for the impatient, but not really difficult, either.

Despite being careful, during my handling of the module I managed to damage one of the SMD transistors, and had to replace it.  So I would recommend a soft touch, which might rule out power tools.

A little dab of CA gel on each corner put it back together.
 

Offline T4P

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Re: UT61E Auto Power Off Modification
« Reply #4 on: September 19, 2012, 04:55:10 AM »
Did you guys use a dremel and attack the interface module or what?  :P
I scored the seam around the module by repeatedly dragging a hobby (X-acto) knife backwards across all four sides.  When the scores were deep enough, the module came apart easily with just a little persuasion from a spudger. Not a job for the impatient, but not really difficult, either.

Despite being careful, during my handling of the module I managed to damage one of the SMD transistors, and had to replace it.  So I would recommend a soft touch, which might rule out power tools.

A little dab of CA gel on each corner put it back together.
Xacto knife wasn't working for me so i took out my cordless drill and my small saw bit, worked well and nothing broke. Just sawed a side and used a flat screwdriver to nudge it out ... Everything's intact
http://the4thpin.comeze.com <-- Rants and Reviews! sorry my english  :palm:
 

Online Monkeh

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Re: UT61E Auto Power Off Modification
« Reply #5 on: September 19, 2012, 06:07:54 AM »
I just slid a small (but not flimsy) knife blade in at a corner, glue broke easily.
 

Offline Amarbir[Lynx-India]

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Re: UT61E Auto Power Off Modification
« Reply #6 on: September 19, 2012, 06:19:04 AM »
Dean ,
 Very Very interesting .If i can ever lay my hands on the same i will definately try this out .On the other hand 30 minutes shutdown would kill the battery soon 15 minutes auto power off is more then enough i think imho  .
Regards

Amarbir Singh Dhillon [ Lynx-India ] , Chandigarh [ India ] - > www.lynxdealerstore.com , www.lynx-india.com
Indian Distributor For  [ Autoelectric , Sofitech , IDEOfy ,Peak Electronic Design [UK ] , Anatek And Creatronica ]
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Offline T4P

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Re: UT61E Auto Power Off Modification
« Reply #7 on: September 19, 2012, 04:03:32 PM »
Huh? In sleep the chip draws next to nothing? (2.5uA-5uA)
And in operation without RS232 on would be more like measured in uA instead of mA
I already posted my findings on the UT61E thread and that's the fact. RS232 is always on without the mod and chews power
http://the4thpin.comeze.com <-- Rants and Reviews! sorry my english  :palm:
 

Offline torr032

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Re: UT61E Auto Power Off Modification
« Reply #8 on: October 08, 2012, 07:33:23 AM »
Is there perhaps a way to modify hold button for example and to force it in the standby mode?
 I don't find it's pretty convenient to turn knob all the way from one side to another, one single on/off button is more useful.
 

Offline DeanA

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Re: UT61E Auto Power Off Modification
« Reply #9 on: October 09, 2012, 06:15:20 PM »

I didn't have a 3mm IR LED, so I used a clear red high-efficiency LED in the RS232 interface module. I used a junkbox photo-transistor in the meter, affixed to the circuit board with some plastic-repair putty.  This keeps from having fiddly little wires connecting the two halves of the case.  It all works nicely.  Data output is enabled immediately when the software turns on the RS-232 handshake lines.

You did a nice neat job of the meter modification, good idea keeping the photo transistor on the PCB too.

Regards,
Dean.

Offline onlooker

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Re: UT61E Auto Power Off Modification
« Reply #10 on: October 20, 2012, 12:20:16 PM »
This is what I did to my new UT61E.  I think it is a simple and good DIY to share. What it does, in addition to the usual APO DIY, is to provide manual power on/off controls at any ON positions of the rotary switch without turning the switch (as other had already asked).

----The operations:

1). When the meter is on, pressing "hold" for 3 seconds to turn the meter off.

2). When the meter is off, pressing "range" to turn it on.

3). The normal "hold" and "range" functions are retained.

4). The APO DIY worked better (smaller off current).

5). Switching the rotary from "OFF" to "V" no longer turn on the meter. I do not feel the need to to retain this function, but if desired probably adding a cap somewhere should have it work again.

----The performance:

1). The off current is about 0.01uA.

In fact, the usual APO DIY by itself has severe problems in that the power off current is about 170uA (my test). For a 200mAh battery, this translates to about 1.5 month power retaining time without using the meter. To give an idea about how small 0.01uA is, it could be mentioned that the leak current of a Li battery with 10 years of shelf life is around 1uA.

2). The burden voltage is about 0.2mV.

3). This power on/off ctrl worked properly even when the battery is < 3V (did not test the meter accuracy at this voltage).

----The making:

Except for the Si4562, all other parts are taken from junk PCBs I had (a few).  That is why you see SMDs of different sizes. I bought Si4562 on ebay for about $0.35 each, but I had to buy 10 for this price. I also made a few goofs: cut a wrong trace on the meter PCB; broke a leg of the IC; a few wiring changes after soldered it to the meter and along the way burnt a corner of the res array.

Altogether, 2 traces on the meter PCB needs to be cut: the VB+ trace and the "range" button trace. The board needs only to be about 4x5 pads in size.

If you want to try this, make sure D1 has enough forward voltage drop or simply place 2 diodes or a zenor instead.

On a related note, for the APO-data link part of the DIY, the pull up resistor is not really needed. According to the datasheet, the RS232 pin was internally pulled up with a short current about 10uA. One can regard this as a resistor of a few hundred k connected to the positive voltage (~3V) rail. I used the photoresistor+red LED approach without the extra resistor.


« Last Edit: October 21, 2012, 01:01:37 AM by onlooker »
 

Offline onlooker

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Re: UT61E Auto Power Off Modification
« Reply #11 on: November 21, 2012, 01:38:34 PM »
This is the version 2 of the auto/manual power switch schematic.  The motivation was simple: After watching Martin Lorton's video, I realized that there was a hidden function when holding down the "hold" button for a few seconds and, hence, I wanted to remove the use of the "hold" button. Along the way I also changed the schematic.

With the new schematic, manual power on/off was done with the same button. My preferred choice was the yellow VAHz button. The key points in my last email remained true.

I wanted to come up with a schematic that does not need to cut the button trace. But, with the parts I have and a limited time to experiment, it either has too large a power-off current (a few uA) or can't be switched reliably. On the other hand, at least, the new schematic does work.
 
 
 

Offline dr_p

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Re: UT61E Auto Power Off Modification
« Reply #12 on: April 21, 2013, 07:21:42 AM »
Just received my UT61E from Franky the other day. I decided I don't need a backlight on every meter, so I'll just do the "Auto power off" hack.


I did everything you guys did, but I used a photoresistor instead of a phototransistor. This I think is critical to what follows. Upon reassembly, the meter kinda froze when the optical port was exposed to light. All digits are off, but it keeps going through the functions.


I did some measurements and I think I found a big problem in your connections: the VB- you considered to be the positive pin of C33, but that is +6V. The chip is powered by 3V, and that is the voltage on the positive terminal of C31. So I reconnected everything and it works like a charm. I think your design pulled pin 111 lower than VB-, but some of the difference (0.7V) fell on the phototransistor, so it kinda worked.


What do you guys think?


[photo removed]

edit: I just noted Satan's quartz crystal :) )
« Last Edit: April 21, 2013, 08:34:40 AM by dr_p »
 

Online Monkeh

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Re: UT61E Auto Power Off Modification
« Reply #13 on: April 21, 2013, 07:57:33 AM »
You need to check the schematic. Negative side of C31 is V-, positive side of C33 is V+. Between them is GND.
 

Offline dr_p

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Re: UT61E Auto Power Off Modification
« Reply #14 on: April 21, 2013, 08:43:22 AM »
Yes, you are right about the capacitors. I removed the previous photo, since the captions were wrong.


But still, datasheet says pin 111 should be pulled to V- to enable serial comm, but doesn't say it has to be pulled to V+ to be idle.


Since the datasheet says "the HIGH an LOW voltage levels correspond to DGND an V- respectively" (Serial data output, p.21), maybe an inactive pin 111 is tied to DGND, so to the positive of C31.
« Last Edit: April 21, 2013, 08:45:30 AM by dr_p »
 

Online Monkeh

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Re: UT61E Auto Power Off Modification
« Reply #15 on: April 21, 2013, 08:51:39 AM »
You may be right, however, I haven't had any issues with mine.
 

Offline dr_p

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Re: UT61E Auto Power Off Modification
« Reply #16 on: April 21, 2013, 09:28:16 AM »
so here's the way it worked for me:


 

Offline rolandpenplotter

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Re: UT61E Auto Power Off Modification
« Reply #17 on: January 19, 2014, 09:14:05 AM »
Hello :)

I've just taken my UT61E apart in order to perform this mod, but I need some clarification which is not provided:

Where the track emerges out from the IC on pin 111, there is a via immediately where the track emerges from the IC; do I cut the trace *BEFORE* the via, or after the via, halfway across the loop to V- ?

If someone could make this crystal clear, I'd appreciate it :)

Thanks a lot folks :)


PS: There's a MUCH easier way to achieve the functionality provided by this mod:

1/ Put a magnet inside the RS232 head

2/ Glue a normally open (N/O) reed switch inside the meter, exactly in the area where the magnet will be when you connect the lead to the meter's recess, cut the track as per this guide, and connect the ends of the reed switch to the pins "111" and the "V-" pin, the trace between which, you have just cut.


;)
« Last Edit: January 19, 2014, 09:22:27 AM by rolandpenplotter »
 

Offline DeanA

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Re: UT61E Auto Power Off Modification
« Reply #18 on: January 19, 2014, 12:28:23 PM »
Hi,
You need to cut the track before the via so that pin 111 only goes to your switch (whatever you are using, phototransistor, LDR or reed switch).
Regards,
Dean

Offline rolandpenplotter

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Re: UT61E Auto Power Off Modification
« Reply #19 on: January 19, 2014, 12:33:26 PM »
Hi,
You need to cut the track before the via so that pin 111 only goes to your switch (whatever you are using, phototransistor, LDR or reed switch).
Regards,
Dean

Thanks Dean, you're a star mate :)
 

Offline rolandpenplotter

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Re: UT61E Auto Power Off Modification
« Reply #20 on: January 20, 2014, 07:08:00 AM »
I've just messed up my meter :'(

I was under the magnifier, preparing the tinning of the lead for the enamelled wire to pin 111, and a blob of solder wicked onto the pins... ARGH!

I tried and tried to suck off the solder, even using a solder sucking tool and by dropping a bigger blob of solder across the mess, and then sucking it off (this is all @ 350 degrees) and NOTHING works; a couple of the pads look a bit skewiff too, bummer!

To compound it, I have NO solder wick at all - I've never had it.

Anyone fancy a cheap, brand new UT61E for a minor repair? I'm just gonna buy a new one I think (well, how I feel right now I am):


 

Offline Legit-Design

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Re: UT61E Auto Power Off Modification
« Reply #21 on: January 20, 2014, 07:15:43 AM »
I've just messed up my meter :'(

I was under the magnifier, preparing the tinning of the lead for the enamelled wire to pin 111, and a blob of solder wicked onto the pins... ARGH!

I tried and tried to suck off the solder, even using a solder sucking tool and by dropping a bigger blob of solder across the mess, and then sucking it off (this is all @ 350 degrees) and NOTHING works; a couple of the pads look a bit skewiff too, bummer!

To compound it, I have NO solder wick at all - I've never had it.

Anyone fancy a cheap, brand new UT61E for a minor repair? I'm just gonna buy a new one I think (well, how I feel right now I am):

http://farm3.staticflickr.com/2824/12037402066_4d3678c352_b.jpg

Buy wick, buy flux -> profit!

Practice with some non critical/broken boards first. Practicing first is the best way to learn and succeed. Nothing is lost yet.
 

Online Monkeh

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Re: UT61E Auto Power Off Modification
« Reply #22 on: January 20, 2014, 07:20:37 AM »
 

Offline Legit-Design

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Re: UT61E Auto Power Off Modification
« Reply #23 on: January 20, 2014, 07:41:12 AM »
There is still pins left on the package and tracks on the pcb. Nothing that isn't too hard to fix. Just need to take a step back and make everything work properly, proper tools and all that. Good soldering iron with adjustable temperature, no more lifted pads. With proper technique and tools no force is required. Maybe start with EEVblog soldering tutorials. Get old computer motherboard or sound/display card and start soldering.
 

Offline rolandpenplotter

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Re: UT61E Auto Power Off Modification
« Reply #24 on: January 20, 2014, 08:34:38 AM »
There is still pins left on the package and tracks on the pcb. Nothing that isn't too hard to fix. Just need to take a step back and make everything work properly, proper tools and all that. Good soldering iron with adjustable temperature, no more lifted pads. With proper technique and tools no force is required. Maybe start with EEVblog soldering tutorials. Get old computer motherboard or sound/display card and start soldering.

Hello :)

I'm 38 and have been soldering since I was 5, on production lines and in TV repair (no, I wasn't working on a production line at 5 years old ^_^).

It's not my soldering that was the issue; I can solder in my sleep. I have a temp controlled anti-static iron - it was that I was rushing and not focusing on the task at hand, and I didn't have any wick or flux. Ah well, sold it now so it's now a non-issue, but thank you for replying.

Maybe I'll save up for a better UNI-T model with APO and backlight, like the UT71E :)
 


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