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Type: Posts; User: pjmelect
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29th October 2019, 04:10
Thread: PC based Oscilloscopes
by pjmelect- Replies
- 11
- Views
- 1,189
Closed: Re: PC based Oscilloscopes
The software for some of these PC based oscilloscopes is often not very good, as the writer of these programs have probably never actually used them in practice. I would save my money and get a good...
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12th October 2019, 23:57
Thread: HP 54520A Blown Fuse Problem
by pjmelect- Replies
- 40
- Views
- 3,313
Closed: Re: HP 54520A Blown Fuse Problem
I would give the power supply to someone who knows how to fix power supplies. If you want to try and fix it yourself, then from what you have said there maybe no fault with the power supply, rather...
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7th October 2019, 02:57
- Replies
- 5
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- 721
Closed: Re: Need of Equivalent IC for SST89E51RD-40-C-PIE
You can still buy this chip why do you need the equivalent?
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2nd October 2019, 17:19
Thread: SD card - pull-ups required?
by pjmelect- Replies
- 6
- Views
- 662
Closed: Re: SD card - pull-ups required?
I have used an SD card without any pull ups. But depending on the micro used this may cause extra current to be drawn when no SD card is present. If in single bit mode (SPI) the three unused SD card...
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2nd October 2019, 04:51
Thread: SD card - pull-ups required?
by pjmelect- Replies
- 6
- Views
- 662
Closed: Re: SD card - pull-ups required?
The pull-up resistors are for protecting the CMD and the DAT lines against bus floating when no card is inserted. So if the SD card is permanetly fitted, pull-up resistors are not needed.
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25th August 2019, 01:17
Thread: ATX power supply switch
by pjmelect- Replies
- 5
- Views
- 580
Closed: Re: ATX power supply switch
On an ATX power supply connecting the PS_ON pin to ground will turn on the power supply, when the PS_ON pin is disconnected from ground the power supply goes off. Logic on the motherboard keeps the...
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21st August 2019, 03:51
- Replies
- 5
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- 1,504
Closed: Re: How to measure differential signals using an Oscilloscope
On older oscilloscopes you invert one channel and sum the two channels. One problem with doing this is that the bandwidth is drastically reduced to around 1Mhz depending on the scope.
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7th August 2019, 17:46
Thread: HP 54520A Blown Fuse Problem
by pjmelect- Replies
- 40
- Views
- 3,313
Closed: Re: HP 54520A Blown Fuse Problem
It is unlikely that that part would cause the problem of the fuse blowing after a minute. It is a inrush suppressor so that after a minute its job is done and no possible fault with it will cause the...
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7th August 2019, 15:07
Thread: HP 54520A Blown Fuse Problem
by pjmelect- Replies
- 40
- Views
- 3,313
Closed: Re: HP 54520A Blown Fuse Problem
With this type of fault, you will have to reduce the circuit to find the fault. first try removing R13 and R14 and see if the fuse still blows. If not reconect R13 R14 and disconect CR24, and see if...
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1st August 2019, 10:35
- Replies
- 2
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- 3,063
[SOLVED]Closed: Re: [moved] How to fix Windows 10 Error? (copying files from network drive)
This error is caused by a corrupt file system either on the networked drive or on the system drive; you should do a system file check on both drives.
Another possibility is that you are getting... -
25th July 2019, 03:51
Thread: Low drop voltage regulator
by pjmelect- Replies
- 8
- Views
- 801
Closed: Re: Low drop voltage regulator
The AMS1117 has a dropout of 1.1V at 0.8A, at 50mA the dropout is much less.
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24th July 2019, 03:27
Thread: Low drop voltage regulator
by pjmelect- Replies
- 8
- Views
- 801
Closed: Re: Low drop voltage regulator
What about the AMS1117 3.3V ? I as well as many others sell them on eBay for not much money. As wwfeklman said it is important to use the manufacturer’s recommendations as to the input and output...
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15th July 2019, 02:16
- Replies
- 2
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- 1,326
[AVR]Closed: Re: Proteus: internal Exception: access Violation in module 'UNKNOWN'
Does your school have a licence for the ATMEG CPU I am assuming that your school has a genuine version of Proteus.
PIC and ATMEG CPU’s require different licenses which are very expensive. -
3rd July 2019, 00:02
- Replies
- 3
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- 632
Closed: Re: I have problem with my proteus 8.4 simulation
Often this type of error is caused by missing grounds, post your Proteus circuit if you want further help.
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23rd June 2019, 01:13
Thread: Electroncis degree website blocked..why?
by pjmelect- Replies
- 4
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- 6,037
Closed: Re: Electroncis degree website blocked..why?
Instead of starting the addres with https: use only http:
This now works. -
4th May 2019, 06:09
- Replies
- 10
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- 1,883
Closed: Re: input impedance to ADC pin on PIC16F18856
I disagree, the 470nF capacitor effectively gives an impedance of zero ohms as far as the input to the ADC is concerned, the voltage of the 470nF capacitor voltage is reduced by the charging of the...
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2nd May 2019, 08:06
- Replies
- 10
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- 1,883
Closed: Re: input impedance to ADC pin on PIC16F18856
If the resolution of the A-D is 12 bits then the capacitor needs to be at least 4096 X 5pf to get 1 bit resolution which is just over 20nF I would suggest the use of a 47nF capacitor. As for the...
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2nd May 2019, 04:30
- Replies
- 10
- Views
- 1,883
Closed: Re: input impedance to ADC pin on PIC16F18856
As long as the sampling rate is low enough then what you sugest will be fine. As the sample capacitor is only 5pF 470nF may be more than you need. Don't forget about input leakage though.
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24th April 2019, 03:49
- Replies
- 3
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- 468
Closed: Re: lcd display problem with unclear characters
The voltage of a LCD is critical if the 5V is down by only a few hundred milivolts can result in no display or very bad contrast on most displays. If you increase the supply voltage you will need a...
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19th April 2019, 06:53
Thread: Matching transistors 2SA899/2SC1904
by pjmelect- Replies
- 2
- Views
- 469
Closed: Matching transistors 2SA899/2SC1904
I have a number of 2SA899/2SC1904 transistors that I am going to sell on eBay, I think that they will sell faster and for a better price if I were to sell them as matched pairs. I think that for a...
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3rd April 2019, 03:36
Thread: problem with proteus
by pjmelect- Replies
- 3
- Views
- 384
Closed: Re: problem with proteus
Yes you could tri state one or the other by setting the pin to an input, but how does one chip know when it is safe to put its pin to output, as there is no other communication between the chips. You...
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2nd April 2019, 04:00
Thread: problem with proteus
by pjmelect- Replies
- 3
- Views
- 384
Closed: Re: problem with proteus
Can you connect two txd pins together?
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31st March 2019, 01:49
- Replies
- 7
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- 531
[PIC]Closed: Re: PIC16F877A correct wiring and the external clock?
You have not defined the configuration bits. Proteus may not care about this, but the hardware does.
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20th March 2019, 03:28
Thread: AD9851 module function genertor
by pjmelect- Replies
- 3
- Views
- 530
Closed: Re: AD9851 module function genertor
You could always buy a pre programed PIC on ebay to drive the AD9851 module, you may find the programming required to calculate the data a bit dificult.
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22nd February 2019, 08:17
Thread: SD card multi block read
by pjmelect- Replies
- 6
- Views
- 1,283
Closed: Re: SD card multi block read
Another funny thing that I have noticed is that I have read the CSD values for 5 different SD cards from different manufacturers and I have got the following values for the access time.
128MB...
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