Hi Everyone
With the analogue outputs set at max and no load connected I am measuring 2 volts max.
The manual states 0 to 5 volts.
Can anyone please help me with this?
The rest of the the board works fine.
I am not an electronic genius so simplicity is the keyword.
Many thanks.
Do the analog ports show the full range 0…255 if you turn the attenuator potentiometers with SK2 and SK3 installed?
Regards,
Jan
Hi Jan
Thanks for the reply.
Yes they do, but I didn’t know that these affected the analogue outputs.
[quote=“RiichardMS”]Hi Jan
Thanks for the reply.
Yes they do, but I didn’t know that these affected the analogue outputs.[/quote]
Oh, I misread, you meant the analogue outputs, not the inputs. My mistake.
The analogue outputs should indeed range from 0…5V. What does not have a voltage are the digital and PWM outputs as they are open collector (acting like a tiny relay with polarity).
Unfortunately this forum does not allow picture uploads. Can you take sharp high resolution pictures from both sides of the board, upload them to a free picture hosting site and post links here?
Regards,
Jan
Thanks Jan.
Can you suggest a hosting site as this is not normally something I do. Alternatively can I email them to you?
Regards.
Photobucket should do.
Jan
OK will do, have to be tomorrow.
Many thanks.
Hi Jan
Here is the link to the pictures:-
s1292.photobucket.com/user/richa … ent&page=1
Hope they will do.
Regards
Hi Richard,
the soldering and components sides look both good. No obvious assembly errors there and very nice soldering work. Congratulations on that.
I presume that you don’t have access to an oscilloscope, but do have a multimeter/voltmeter. With analog output 1 (DAC1/PWM1) full on, what are the voltages at the following pins:
IC3 pin 13
IC1 pin 4
IC1 pin 12
IC1 pin 14
Does the LED for PWM1 (LD9) appear as bright as the Power LED (LD11)?
Regards,
Jan
Hi Jan
These are my results:-
IC3 pin 13 - 4.5v
IC1 pin 4 - 4.8v
IC1 pin 12 - 1.0v
IC1 pin 14 - 4.5v
The pwm led is as bright as the power led;
I measured the dac output again it is now 4.5v so I don’t know what happened there!
However, I connected a 5 volt motor across dac out and gnd. nothing, so I replaced the motor with a led and this was about half the brightness it should be (nowhere near as bright as the onboard led).
This is all rather confusing.
Regards.
Electronics does have a bit of a learning curve at the beginning. Don’t be intimidated by it.
[quote=“RiichardMS”]Hi Jan
These are my results:-
IC3 pin 13 - 4.5v
IC1 pin 4 - 4.8v
IC1 pin 12 - 1.0v
IC1 pin 14 - 4.5v
The pwm led is as bright as the power led;
I measured the dac output again it is now 4.5v so I don’t know what happened there![/quote]
IC1 pin 12 should read the same as IC3 pin 13. Possible you have what we call a “cold solder joint” anywhere along that connection. touching things with the leads of your voltmeter may have temporarily made the connection. You can easily reheat the pins for IC1 pin 12, IC3 pin 13 and resistor R13 to make sure.
The analog outputs are not meant to drive something like a motor. There are 1.5 kilo Ohm current limiting resistors (R14 and R15) protecting DAC1 and DAC2. They protect IC1 from being damaged by precisely what you tried for a test.
An electric motor is by nature a device with rather high current consumption. While this is not entirely technically accurate since a motor is an inductive load and not a resistive one, something like the equivalence of 5-10 Ohms is typical for small toy motors. Without going into the math behind it, the 1K5 resistor on the K8055 board builds a voltage divider with whatever load you connect to the analog output. With a 10 Ohm load the load will not see more than 33 mV.
The LED isn’t a good test object either. It is typically a semiconductor. As such it is normally used with a current limiting resistor according to how much current it needs, the supply voltage and how big its voltage drop is. Again without going into all the math you can see in the schematics of the K8055 itself that all the LEDs on the board have a 1K current limiter in series. And those are really small, low current LEDs. Your average “variety pack” red LED has a voltage drop of 2V and needs about 20 mA. That would lead us to a current limiter of 150 Ohms (I’d use 220 to error on the safe side). The 1K5 in the analog output is way too high.
Both, the motor as well as the LED, should be driven through the PWM outputs. For anything but a small toy motor you will need additional components like power transistors. There are plenty of examples on this topic on this forum. Don’t forget the current limiter for the LED!
The analog outputs are meant to drive high impedance “control” inputs of other devices such as voltage controlled amplifiers, filters or light dimmers. Test objects to play with are hard to find in an average household.
Regards,
Jan
Hi Jan
Many many thanks for the time and help which you you have given men.
I have taken on board all you have and will continue to persevere with this.
The world of electronics is fascinating and it is nice to know that people such as yourself are willing to give their time and expertise to novices such as me.
Cheers and regards, Richard.