Uni-T UT61E backlight mod with touch sensor [tutorial]

[TacticalSnacks]

I order MCP1703 - 4V, TTP223 ( two different boards ). I receive MCP and one TTP223 ( red board ).
From TTP223 it is enough output amperage to turn on two LED's in parallel ? I suppose NO. In specs are 8mA !
I will try on bench before installing on to UT61E.

No, the TTP223 shouldn't be used to source or sink current. Instead, use a transistor tied to the TTP223's output to drive your LED's. See schematic here.

[Mike60]

[quote author=TacticalSnacks

No, the TTP223 shouldn't be used to source or sink current. Instead, use a transistor tied to the TTP223's output to drive your LED's. See schematic here.
[/quote]

NO. I don't need to install supplementary transistor. It is enough current from TTP223. From data sheet theorethically 8mA. With two leds i have 11.7mA. MCP1703-4V. I try before with another resistors ( now it is 47ohm ) but current remain the same. Maybe it is output current protected.
I like this brightness more like my another two DMM because are not white/blue color.   
I need to do something better with touch-sensor.
Regards
Mike

[Pacote]

Can I use a cheaper voltage regulator for this like this one?

http://www.ebay.com/itm/10-pcs-AMS1117-3-3V-1A-Voltage-Regulator-AMS1117-3-3V-SD9-/131816681209?hash=item1eb0e2eef9:g:YscAAOSwH71XOccK

[mariush]

Yes, you can use those regulators, they're generic 1117 linear regulators.

Note however that they output 3.3v only as long as the input voltage is higher than about 4.3v, the voltage dropout is 1v, much larger compared to MCP1703. Also, this particular series of regulators is kind of picky about the output capacitors, it prefers an electrolytic capacitor but you can use a ceramic capacitor as long as you put an extra resistor (something like 1-3 ohm) in series with the output capacitor.
So basically it's either use a larger electrolytic (compared to ceramics) or use a tantalum capacitor (expensive) or you use a ceramic capacitor and an extra ceramic resistor on the board.



 

[Pacote]

All my stuff arrived and I did the full mod but no power...

If I solder the 9v from the pcb to the MCP1703 I get a dead multimeter...

I bought these...

http://pt.aliexpress.com/item/Free-Shipping-10PCS-MCP1703-3-3V-SOT-23-MCP1703T-3302E-CB-original-authentic-100-new-original/32639467660.html

Maybe the pinout is different somehow?


EDITED:

Yep, all working now

The chip I purchased has a different pinout. Soldered in again, correctly now and everything is working \o/

[Edit2]

Well... Something changed... because its measuring my 5V and 12V power supply as 5.12v and 12.22v

How can I try to calibrate it?

[demonmk]

i did this but my multimeter stoped work pls help me guys what to do now i remove this system and still show me open line OL on all function how to fix this thanks

[Maxlor]

Show us some photos of your modifications.

[joeqsmith]

Or do it with a photo sensor.

https://youtu.be/S36LfKmSjKw?t=329

[hugo]

Or do it with a photo sensor.

https://youtu.be/S36LfKmSjKw?t=329

Brilliant ... pun intended

[demonmk]

Here is some picture but i removed the system... first i want to make it work without backlight then maybe i will try to install backlight again. for now im scared that i burn my new multimeter i hope u will help me guys how to fix this thanks

here is video: https://youtu.be/2HYyrsPP9jI

[joeqsmith]

Perhaps no ESD projection while you worked on it?   Looks like some solder on the side of the one resistor.  Perhaps there is solder in other places where it should not be.   Maybe all that wire jammed in there is preventing one or more switch contacts from making proper contact.

On the plus side, it's a cheap meter.  You can always get a new one and start over. 

[Maxlor]

Since we're trying to diagnose a fault here, we really need to see the area that you modified on the PCB too, not just your LEDs.

[bourinov]

I just modified my UNI-T 61 - everything works well. I have green light... Thank you!

[The_Boots]

I know this is an extremely old thread, but I still wanted to thank you! It worked well and I learned a lot. I had to make a few changes (different ttp board, got a little pcb to stick the regulator on cause it's so tiny), which makes it a very tight fit, so I'll probably keep tinkering with it. It looks great though!

[seanspotatobusiness]

Which areas of the PCB do I need to avoid when threading my led power wires from the back to the front?

[Pluscrafter]

Will the CAT rating remaining and could you use normal LED's insetead of SMD LEds?

[Maxlor]

Will the CAT rating remaining and could you use normal LED's insetead of SMD LEds?

CAT rating: well, no, if you mod the meter, it falls to you to determine how safe the meter is afterwards. But... this isn't the sort of meter you want to be using if you're worried about CAT ratings, in my opinion.

normal LEDs: they'll work if they're small enough. there's not much height available, around 1.5mm iirc? If yours are small or thin enough, sure, it'll work.

[jayjr1105]

Or do it with a photo sensor.

https://youtu.be/S36LfKmSjKw?t=329

Can you tell me/us what parts you used.  Any regulators?  Resistor values and just an NPN and PNP?

[jayjr1105]

On another note.  I finished phase 1 of the mod.  Right now I have backlight if the meter is on.  I can't decide if I want to go photoresistor or touch sensor.

I've heard Blue isn't the best color for this because of the higher voltage drop but I love the contrast with the red.  I also have them in series using a tiny buck converter dialed down to 6v.  I'll probably move this down to parallel depending on which phase 2 I decide.

Any recommendations?

BTW, the buck converter I used. 
https://www.ebay.com/itm/10pcs-Mini360-3A-DC-Voltage-Step-Down-Power-Converter-Buck-Module-3-3V-5V-9V-12V/132416658988?hash=item1ed4a5de2c:g:djUAAOSwGPNcUg0c:rk:7:pf:0
Would this be more efficient than a mini regulator?