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DIY SSR with '555
bvwelch
Top  #26 Print Post
Posted on 01/21/2008 8:11 PM
The puzzling part is why it would be better in your circuit. I think it probably means that the linear pot was covering a much wider range than was useful to you.

Bill
 
bvwelch
Top  #27 Print Post
Posted on 01/26/2008 1:10 PM

Quote

bvwelch wrote:
I've found a better approach to using the '555. I'll be testing this out on the bench, and updating the schematic accordingly.

The advantage to this new circuit is that you can keep the period of the timer circuit constant, and vary only the duty cycle. With the old circuit, both the duty cycle and the period of the timer changed at the same time, which really made it hard to choose the best values for the resistor, potentiometer, and capacitor.

You can read about it here. It is a nice tutorial about the 555 as well.

http://www.dprg.o...index.html

Bill


I may start a different thread on this subject, but the new approach works well. I'm using it, like Doug Strait's mods, to control the Wearever Pumper with DC. The new '555 circuit really works well.

Photos at my web site, look for "boost..." they are over-size for this web site.

http://bvwelch.co...

Bill
 
seedlings
Top  #28 Print Post
Posted on 01/26/2008 8:55 PM
Here, Bill, I resized your pics! Looks good. Could you describe in your own words how this circuit helps? Thanks!

CHAD

i206.photobucket.com/albums/bb54/seedlings/booster1.jpg
i206.photobucket.com/albums/bb54/seedlings/booster2.jpg
i206.photobucket.com/albums/bb54/seedlings/booster3.jpg
Roaster: CoffeeAir II 2# DIY air roaster
Grinder: Vintage Grindmaster 500
Brewers: Vintage Cory DCU DCL, Aeropress, Press, Osaka Titanium pourover
 
bvwelch
Top  #29 Print Post
Posted on 01/26/2008 11:05 PM
Thanks Chad!

There a three things going on with this photo: 1) Doug's idea was to put the mods inside the pumper -- it is big and roomy in there. So what you see laying on my bench, I plan to install inside the popper.

2) the '555 uses that approach we discussed above, where the frequency or period of the pulse-width-modulation is constant, and only the duty cycle varies when you twist the knob. With the initial circuit, both the frequency and the duty cycle varied continuously, which made it complicated to find good values of R and C.

3) The pumper, like the Poppery 1, is wired from the factory as a 120 volt AC motor -- not like most modern poppers, which have a 20 volt DC motor. Anyway, the motors in the pumper and the Poppery 1 are actually "universal" motors, which means they can run on DC just as well as AC. And by rectifying the AC into DC, and adding the large "filter" capacitor, you can get about 160 volts DC for the motor, which means you can "boost" its speed, without a transformer. Since it is a DC circuit, the power mosfet is used, instead of a triac. I'll upload a schematic for this soon.

I do plan to try a variation of this idea, on the 20 volt DC poppers. But I'll have to be careful not to accidentally hit them with too much voltage and zap them.

Next I plan to try the new style '555 circuit on my heater triac circuit. It should result in a design that is easier to replicate with whatever R and C values you have on hand.

Bill
 
seedlings
Top  #30 Print Post
Posted on 01/26/2008 11:32 PM
EXCELLENT!s:2s:2s:2

CHAD
Roaster: CoffeeAir II 2# DIY air roaster
Grinder: Vintage Grindmaster 500
Brewers: Vintage Cory DCU DCL, Aeropress, Press, Osaka Titanium pourover
 
seedlings
Top  #31 Print Post
Posted on 02/01/2008 12:42 PM
Hey Bill, could one pot and one 555 control multiple triacs? Like if I wanted three 20amp heat elements... or one one knob to control the heat element triac AND the blower motor triac...

Maybe using a different value for the 220 ohm resistor?

CHAD
Roaster: CoffeeAir II 2# DIY air roaster
Grinder: Vintage Grindmaster 500
Brewers: Vintage Cory DCU DCL, Aeropress, Press, Osaka Titanium pourover
 
bvwelch
Top  #32 Print Post
Posted on 02/01/2008 1:21 PM
Chad,

You're making me nervous. :-)

I think I would just connect three different resistors to the output of the '555.

I don't see why you would want to control the heat and fan with the same knob.

By the way, I'd recommend going to the improved '555 circuit if you want to do a motor. And actually, use a different driver chip (one of the others that I sent you). Let me look at my schematic to make sure which one I chose. Then it will be like your router speed controller.

You could use the "dimmer-style" driver chip for both the motor/fan and the heat. We'll have to change the thread to DIY router speed controller, since SSRs seem to be the zero-crossing kind.

Clear as mud? Ask questions, and I'll write back when I have more time.

Edit: I took a quick look-- I haven't tested the non-zero crossing triac drivers yet. Sorry. I'll let you know when I get a chance to try them.


-bill
Edited by bvwelch on 02/01/2008 5:21 PM
 
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