next topic »

[Reply #45 on:]

thank ill let you know how i get on

[Reply #46 on:]

Alrighty then.

I revised the circuit (attached) and the test "sketch" (also attached).  I used Port Manipulation ─ Bam!, all bits at one felled swoop.

Now, (either way) more than one input can be on at once.  [The other ckt could, too, but the results would be off].  Here, it approximates a 3-bit DAC (7 levels and '0').
I have a bunch of 20kΩ resistors and made good use of them here.

1.83V, 3.32V, 4.58V, 5.56V, 6.48V, 7.27V, 7.69V
Not phenomenally linear, but I can live with it.

***
No demo video this time, but here's a pic of the staircase as seen on the oscilloscope ─

I cant see a sketch attached, also would it be possible for the range to start at 2 and go up to 10v. as this is the operating range of the triak.

[Reply #47 on:]

This is my take on the problem. Make the PWM signal into a 12V signal, then smooth it, finally drive the SSR unit with an emitter follower.
The diode in the base takes 0.7V off and the emitter base voltage another 0.7V, giving you just over 10V as the maximum. This will be fine, and you will get finer control than just using a three bit A/D.

[Reply #48 on:]

I cant see a sketch attached,
I'd swear that I did that.  They're here for sure.
also would it be possible for the range to start at 2 and go up to 10v. as this is the operating range of the triak.
I'm about done on design work.  If you reduce the value of the gain-setting resistor (the 6.8kΩ [use a pot!]), which will increase the gain a bit, you should be able to dial it right so 001 == 2V and 111 == 10V or so.  Your opamp supply will have to be about 12V.

Grumpy Mike,
How about some data?

[Reply #49 on:]

How about some data?

Sorry don't know what you mean.

[Reply #50 on:]

Grumpy Mike,
Have you any test results to share (in re. Prop SSR.pdf)?

[Reply #51 on:]

No, why should I?
I have drawn a circuit, it wouldn't dare not to work.

[Reply #52 on:]

This is my take on the problem. Make the PWM signal into a 12V signal, then smooth it, finally drive the SSR unit with an emitter follower.
The diode in the base takes 0.7V off and the emitter base voltage another 0.7V, giving you just over 10V as the maximum. This will be fine, and you will get finer control than just using a three bit A/D.

this is giving me 15v at the controller and the pwm does not change the voltage

[Reply #53 on:]

Do up what you can from you have, learn as you go along.
I knew that it'd work, but I breadboarded it.  
I added a selection, a diode into 20k.
I recorded it with the camera ─

You can see the D13 LED reflected off the black project box.
The meter shows "0 - 20 - 40 - 60 - ... 120" which is == 0V - 2V - 4V- ... 12V.  It's on the op-amp's output.
I've attached my test "sketch", it uses D10, 11, 12, 13. (It was easier to cable those over.)

got this working great I just need to up the output voltage a bit.


done it, changed the 10k for a 6k8 I now have 10v max.

[Reply #54 on:]

this is giving me 15v at the controller and the pwm does not change the voltage

There is no way on earth that you can have that result. With only 12V on the pull up switch you just can't get 15V at the controller, unless you have found a way to break the laws of physics.

[Reply #55 on:]

this is giving me 15v at the controller and the pwm does not change the voltage

There is no way on earth that you can have that result. With only 12V on the pull up switch you just can't get 15V at the controller, unless you have found a way to break the laws of physics.

sorry typo it is 1.5v, but I cant get the voltage to change with the pwm. constant 1.5v

[Reply #56 on:]

my apologies grumpy mike my fault need to get my glasses changed, it is working like a dream with pwm.
you are the man.

[Reply #57 on:]

This is my take on the problem. Make the PWM signal into a 12V signal, then smooth it, finally drive the SSR unit with an emitter follower.
The diode in the base takes 0.7V off and the emitter base voltage another 0.7V, giving you just over 10V as the maximum. This will be fine, and you will get finer control than just using a three bit A/D.

After further testing the circuit works fine fading a 100w lamp up and down but when i do an analogue.write at say 255 the lamp goes full brightness for 3 seconds then the lamp goes out with no volts at the controller. It does this through the whole range 0-255. Why am i loosing power after a few seconds, could it be the controller is taking too much current.

[Reply #58 on:]

A value of 255 is on all the time, so it has stopped pulsing. Have you any capacitave coupling anywhere, that could account for it.

[Reply #59 on:]

no it is just the circuit you given which goes straight to the controller, im loosing the will to live with this project.