Skip to main content ↑ ↓
Topic: Parts for Breadboard & Schematic Questions (Read 27624 times) previous topic - next topic

Re: Parts for Breadboard & Schematic Questions

Reply #30 –
1) Yes, the 33KΩ surely looks like a pull-up resistor and does the same thing as the 3.3KΩ resistor, but the pull-up resistor examples I've seen are about preventing an IC input signal from floating (high resistance, 10KΩ+, between Vcc and IC & GND).

How does it work when it connects Vs with IC OUT? If it is suppose to "pull-up" to 5V, it is giving a steady 3.22V.

2) How do you get better receiving sensitivity by adding a 100Ω resistor (R1 in datasheet's application circuit example, and below) between capacitor and diode on Vs/Vcc line (pin 7 of serial port), and increasing the capacitor to 10µF?



3) Found out the circuit doesn't work with IgorPlugXP/Girder if you take out the 3.3KΩ resistor.

Re: Parts for Breadboard & Schematic Questions

Reply #31 –
[quote author="liyin"]
1) Yes, the 33KΩ surely looks like a pull-up resistor and does the same thing as the 3.3KΩ resistor, but the pull-up resistor examples I've seen are about preventing an IC input signal from floating (high resistance, 10KΩ+, between Vcc and IC & GND).

How does it work when it connects Vs with IC OUT? If it is suppose to "pull-up" to 5V, it is giving a steady 3.22V.
[/quote]

The pull-up makes the output pin not float.  It is pulling it toward the supply voltage.  However there is still some resistance between the supply voltage and the output pin which will cause a voltage drop.  When the device is generating a signal, it will be trying to pull the output line low, towards ground.   It order to do that it needs to provide less resistance to ground than the pull-up path.    If you've got both the internal 33K and the external 3.3K pulling out up, combining those parallel resistors means you have a total of 3000 ohms resistance pulling out towards the supply voltage.   So the signal needs to be less than 3000 ohms resistance to pull it down.

Quote
3) Found out the circuit doesn't work with IgorPlugXP/Girder if you take out the 3.3K? resistor.

What's the voltage range on the serial port you are pulling it into?  is it 0-5V?   You are probably fine if the output gets pulled down to 2V or below to indicate the presence of an IR signal.   If it's working what's your primary concern?

Re: Parts for Breadboard & Schematic Questions

Reply #32 –
3) Issue solved, it was the breadboard contacts, I got a 5V reading at the output lead.

Re: Parts for Breadboard & Schematic Questions

Reply #33 –
How do I configure WinPic800 for programming a PIC18F2550 (JDM2)?

I get the following info (Vdd light is OFF):

Opening COM1
Detected -> 18F2550
DEV ID -> 0x1247

(Clock - 4us)

If I read the chip I get only FFFF's and no OSCCAL.

Re: Parts for Breadboard & Schematic Questions

Reply #34 –
The DEVID is a device ID for that PIC chip. It matched with winpic800 expected, so it knows it is a 18F2550.

0xFFFF usually means a blank chip. It could also have code protection enabled if it's a chip from a commercial product.

I'm not sure about OSCCAL or the correct settings, you'd need to look that stuff up in the datasheet:
http://ww1.microchip.com/downloads/en/D ... 39632b.pdf
Got a question? Please ask in the forum for the fastest answers.

Re: Parts for Breadboard & Schematic Questions

Reply #35 –
Program a PIC microcontroller

http://www.diylife.com/2008/02/15/program-a-pic-microcontroller/

Quote
The PIC 16F line requires 13 volts on Vpp, newer 18F PICs use 12.5 volts, and the newest PICs (24F/32F) use 6 volts or less. If you want to program a newer 18F PIC with a JDM2, you should use a diode (D1) as shown in the diagram. This diode will reduce the programming voltage by about .6 volts, leaving a nearly perfect 12.4 volts.

Re: Parts for Breadboard & Schematic Questions

Reply #36 –
I'm wrong :) Get rid of that diode, the programmer can't ground MCLR with the diode in place. I've never used the diode, but I've read of doing it multiple times so I included it in the article.
Got a question? Please ask in the forum for the fastest answers.

Re: Parts for Breadboard & Schematic Questions

Reply #37 –

Re: Parts for Breadboard & Schematic Questions

Reply #38 –
Did you draw that by hand, or is there some kind of virtual breadboard software out there?
Either way, it looks cool.

Re: Parts for Breadboard & Schematic Questions

Reply #39 –
I started with Fritzing, but was limited in the ways it can orient the shapes, so I took the breadboard image from the net and draw the parts. I tried to keep the lengths the same as the real parts, for example, the crystal I used is three-holes long.

Next project, I will see if I can get similar results with another software. Or I'll draw a new breadboard to scale, which will make it easier to scale the parts.

Re: Parts for Breadboard & Schematic Questions

Reply #40 –
This is the JDM2 programmer to flash the PIC (Ian's credit-card size project @ Instructables):