Problem with Inchworm ICD

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I was thinking on doing a PCB for the might be popular LC meter. There is a better 16F628A version. I'd like a frequency & duty counter too if I did it. Might base it on a 16F88 instead. Would also like to see if it's possible to get the internal comparator working in the design.
**broken link removed**
 
Just googled the mondo superprobe - wow! I need to build one of these My next project has just been lined up.
 
I will post the Eagle files in the AM over in projects.

 
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I think this would be a good kit. I like the idea of a probe but finding a ready made case has proved to be difficult.

The EA is a lot more complicated then theSuperProbe which has more functions. Maybe the EA is more accurate. The LED display on the SuperProbe is obsolete and it should be replaced by a LCD if anyone updates it.

I am not crazy about having 4 AAA cells. Given that it uses an LCD display maybe one could use a charge pump. The SuperProbe is powered from the circuit under test which takes another lead.

The SuperProbe has a voltmeter function that I use. I saves having to pull out the volt meter when the probe is already in use. I have also used the RS232 signal generation/injection.

For me a good probe of this sort would be coded in C and have an ICSP connector. That would allow me to customize it to do things like send and receive packets.
 

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Much of the complexity of the Engineers Assistant is the automatic power switching. You could power it off the target and skip the batteries.

I like the LCD too, 2x16 LCD displays are common now. Maybe combine the superprobe and EA... (add a rs232 port too?)

The new 16F886 might be a handy choice.

Ultraprobe?
**broken link removed**

PS it's a cool case, made of PCB with most of the copper etched out.
 
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wow neat. I like that one as well. But I think I'll start with the superprobe first. While were on the subject of probes, a bit off topic, but does anyone else have a list of cool tools to build like the SP and EA
 
jeg223 said:
The kit came with a .22:mu: F cap for the output filter on the 7805 so I replaced it with a 47:mu: F 10V and I made sure
Click to expand...

The kit from me comes with 47uF for output power filter, not .22, please check the C2 in partslist:

**broken link removed**

Actually, there is no .22uF capacitor in the kit at all, I do not even carry such value.

As for the crystal problem, this has been sorted out and after April 5 every crystal has been plugged into live unit and successfully connected to MPLAB. I retested about 30 remaining crystals from previous order and found 5 bad units. Omar was the only customer who reported this problem back to me. I am really sorry about those who had to spend their time troubleshooting the crystal problem and if I can do something to make it up, I will.

All microcontrollers were flashed and succesfully verified in gang programmer with already preflashed OS for PIC16 devices. That procedure would have failed if the unit was bad.

The green LED must be fully on when powered, not dimmed. Dimmed LED suggests that power supply is not working.

The cable must be a straight through 8 wires type, not a RX, TX, GND type sometimes found. Wrong RS232 cable seemed to be a problem for few customers before.

And please, do not start needlesly chaging parts for different types and values. Those who have enough capacity to change the parts do not need to seek assistance in this forum others should stick to the partslist.
 
Interestingly, I submitted this message before and did not show up ... so here it is again.

The kit came with a .22 F cap for the output filter on the 7805 so I replaced it with a 47 F 10V
Click to expand...

There is no .22F (or uF) in our kit and C2 is already 47uF/10V:

**broken link removed**

The problem with crystal was resolved on April 5, thanks to Omar for reporting the problem. All the crystals shipping now have been tested in live unit, which connected to MPLAB.

PICs are flashed on a gang programmer and verified. Bad micro would not pass this procedure.

Verify that your cable is straight through and has all 8 connections. There was few people including myself that had wrong RS232 cable.

Also do not needlessly change the part numbers.
 
I got the internal comparator working as an oscillator on a '628A Bill. It ties up the TMR0 T0CKI pin (RA4) though so I had to setup TMR1 as the frequency counter and I fed the comparator output to the T1CKI pin (RB6). Here's how I setup the comparator;

Code: 
MAIN    movlw   b'00000110'     ;                                 |B0
                                ; b7 = C2OUT                      |B0
                                ; b5 = C2INV                      |B0
        movwf   CMCON           ; turn comparator on              |B0
        bsf     STATUS,RP0      ; bank 1                          |B1
        movlw   b'00001111'     ; RA4=output, RA0-RA3=inputs      |B1
        movwf   TRISA           ;                                 |B1
        movlw   b'01000000'     ; RB6 = input (T1CKI)             |B1
        movwf   TRISB           ;                                 |B1
        bcf     STATUS,RP0      ; bank 0                          |B0
Just need to fabricate a new prototype and finish the software. I was using the serial port and Hyperterminal instead of an LCD.
 

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That's excellent Mike, Creatron is looking for kits as the DIY kits are old news and the Velleman kits are pricy.

I'll try to build a 16F88 version, I'd really like to do something along the Mondo superprobe too.
 
dipmicro said:
Actually, there is no .22uF capacitor in the kit at all, I do not even carry such value.
Click to expand...

The .22uF cap is the same color as the 47uF. I'm sure it just slipped through from your supplier.
I'm getting another crystal tomorrow and I'll let you know if that solves the problem.
 
I replaced the crystal and the board works great. I wrote a quick program and everything seems to be working.

Thanks for all your help everyone.

Jim
 
This crystal problem is like a curse, I will never order from that supplier anymore. I have now a batch from different supplier and tested some 50 units and did not locate a bad piece yet.

Jim, when did you order your Inchworm? Is there anything I can do to make up for the frustration with the crystal?
 
dipmicro said:
Jim, when did you order your Inchworm? Is there anything I can do to make up for the frustration with the crystal?
Click to expand...

I ordered on April 27.
I think shipping to the states costs more than the crystal, so maybe if you could end world hunger...
I'm just happy that everything works now. It's a great little kit.
Thank you
Jim
 
The crystal Jim had was physically tested in another Inchworm built from the exactly same parts.

There is a "right" type for crystals as Microchip allows any crystals and provides ranges of side capacitors. AT cut crystals may require serial resistor (Microchip spec 30292c table 12-2).

I am just thinking loud if those "bad" crystals would work in Inchworm if the capacitors were removed or if serial resistor was installed.

This problem will apear again in other microcontroller projects using crystals because some crystal vendors would not provide specifications and even if they did, people may not know.

In Inchworm case this was my job to make sure that the crystal and C10, C13 were properly selected. I just wonder if anybody has an idea how to verify that crystal is working under optimal conditions (as opposed to marginal ones).
 
The previous message came out as a babble because I was typing it while interrupted several times. I actually would like only to get some feedback on this:

dipmicro said:
I just wonder if anybody has an idea how to verify that crystal is working under optimal conditions (as opposed to marginal ones).
Click to expand...
 
dipmicro said:
The previous message came out as a babble because I was typing it while interrupted several times. I actually would like only to get some feedback on this:
Click to expand...


I would think that only direct measurement with a very high impedence, low capacitance probe on the OSC input pin, measuring amplitude and frequency would be the best test. I guess that once one validated a given manufacture's crystal that you shouldn't have to test each one unless you change vendor or crystal part number.

It's hard to guess if the problem is just poor quality control with that one batch of crystals or if their unpublished specifications were not compatable with the PIC oscillator circuit. Only further testing could determine more.

Lefty
 
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