PID makes lights flicker

[ImpulsiveJames]

Hi, I have a Frankenstein'd Gaggia Coffee espresso machine that is rated for 1370 watts and with the addition of a PID controller, my lights dim about every 2 seconds throughout the house. I was reading a little bit about snubber circuits, but I'm not sure if that's the right way to go or not.

Thanks!

[Andy Chee]

What do you mean by Frankenstein’d? Have you gutted the coffee maker’s control electronics and connected the heating element to your PID?

[IanB]

Hi, I have a Frankenstein'd Gaggia Coffee espresso machine that is rated for 1370 watts and with the addition of a PID controller, my lights dim about every 2 seconds throughout the house. I was reading a little bit about snubber circuits, but I'm not sure if that's the right way to go or not.

Lights dimming is a result of a lack of stiffness in the electrical supply and switching heavy loads on and off. The only practical way to limit the effect is to make the heavy loads switch on and off more gradually rather than suddenly. For example, you could remove the PID controller from the coffee machine and instead use a control scheme with phase angle power regulation instead of on/off control.

[DavidAlfa]

It's barely 6 amps @230V, 12A @110V.
If your entire home flickers, there's something wrong in your electrical wiring.
Try other sockets closer to the electric distribution panel.
Won't be you loading the wiring meant for Illumination, which is much thinner?

[TonyStewart]

If you chose dry relay contacts for the heater control, then I would expect PAR LED lamps to flicker when the power turns off from flyback effects.  A 4.7 nF film cap can fix that.

But if the lights dim for a second every 2 seconds, everywhere in the house, with only 1.5 kW on a separate breaker that's a wiring "load regulation" issue.
But you were not very clear about the dimming part.

[IanB]

It's barely 6 amps @230V, 12A @110V.
If your entire home flickers, there's something wrong in your electrical wiring.

In the USA, it is normal to have lighting and wall outlets on the same circuits. It is also normal to have long runs from the distribution panel with receptacles daisy-chained along it (American houses are bigger than European houses). It is also normal to size the wiring for allowable resistive heating rather than maximum voltage drop. Combine all these factors and you have what many people have experienced, which is that lights dim when an electric clothes iron or a laser printer cycles on and off.

(Or in my case, the whole house dims when my neighbor's A/C switches on.)

[ImpulsiveJames]

Wow, that's a lot of info already!

Let me be wayyyy more specific:

The espresso machine had two thermostats when I bought it (it's from 1985ish), so once the machine was clicked on, power would flow through the heater/boiler until it reached about 220f, then click off until it dropped below 190f or something like that. One of the big improvements to this machine is to add a digital temp probe and add a PID controller to keep the temp as consistent as possible. I've added a few other little things, but not a ton else electrically.

My house is 120v ac and built in around 1978. I'm pretty sure this outlet is very Daisy chained around the outside of our garage and connected to a fridge and a chest freezer.

I was hoping for something simple like adding (I think they're called) in rush capacitors, but apparently you can't do that with AC. I could possibly use a battery backup, but that sounds like a lot of trouble.

So what I'm gathering is I should run a dedicated circuit to a new circuit breaker? I'm really surprised to hear that the other guy's lights flash when their neighbor's air conditioning turns on, I'm not sure if that happens here or not.

[Kleinstein]

How much the lights get dimmer when the voltage drops also depends on the lights. There are now quite different lights and also different variants of LED bulbs in how they regulate the current.

The first think would still be to check if there is somerhing wron in the wiring if the voltage drop too much. Normally a single maybe 15 load should not make a whole lot of difference. So it may still indicate a problem, like a lose wire at the distribution box or maybe a outlet in a daisy chain. So maybe actually measure the drop in voltage. Trying different outputs could be a good idea too - this way one may narrow down the problem area.


A seprate braker / outlet for mainly the coffee machine and maybe a few small uses (e.g. phone charging, radio) may be a good idea. It is anyway a good idea no to have the light on the same GFI string as many other things. One reason to have a seprate braker / circuit for the light is to reduce the risk of standing in the dark from a tripped braker or GFI.

For the regulation, phase angle control is usually only allowed for lowe power as it can mess up the waveform to much. So the preferred regulation is the slow PWM / pulse group regulation like it is likely used.

[ifonlyeverything]

It's barely 6 amps @230V, 12A @110V.
If your entire home flickers, there's something wrong in your electrical wiring.

In the USA, it is normal to have lighting and wall outlets on the same circuits. It is also normal to have long runs from the distribution panel with receptacles daisy-chained along it (American houses are bigger than European houses). It is also normal to size the wiring for allowable resistive heating rather than maximum voltage drop. Combine all these factors and you have what many people have experienced, which is that lights dim when an electric clothes iron or a laser printer cycles on and off.

(Or in my case, the whole house dims when my neighbor's A/C switches on.)

A 250 watt power supply and the PID control loop on my 3D printer's bed is enough to cause the lights in my entire apartment to flicker....

[Doctorandus_P]

You can also go the other way: Improve your lighting so the light output does not vary with variations in your mains voltage. For example use an SMPS power supply to get a low voltage DC, and run the lighting from that. It can also inspire you to make very nice custom LED lighting.

A problem with standard LED lighting is that the circuits are kept very basic. They have for example 50 LED's in series combined with some rectifiing and current limiting. When you put so many LED's in series, it won't have any light output when the voltage over the string is below 80V or so, and when a resistor is used as current limiting the difference in light output is also relatively high with fluctuations of the mains voltage.

You can also do a simple test: Get a decent DMM and stick it's probes into a wall socket and you will see the voltage change in the rhythm of your PID and light flickering.

[DavidAlfa]

A 250 watt power supply and the PID control loop on my 3D printer's bed is enough to cause the lights in my entire apartment to flicker....

250W shouldn't cause anything like this!
As said, try other outlets in the house, seems like a bad connection, maybe a loose terminal block causing arcing or a hotspot.
Not safe either, could catch fire if this is the actual case.

[BeBuLamar]

If you can't keep a 6A load switching on/off without diming your light then it's best to use a PID controller with analog output to control a phase angle SSR. 

[Terry Bites]

The heater's cold resistance will be much lower than it is at full heat. Like 10x or more for a light bulb.
 This makes for a heavy start up current.
Your 9 ohm heater may be only 0.9 when cold and briefly drawing 100A.

To avoid the surge use a slow start scheme. There are pelnty of triac slow start circuits on the interweb. PWM control is easy.

[DavidAlfa]

This is true for an incandescent bulb, but not really for a heater, they stay at pretty much the same resistance either cold or hot, they neither reach 2500°C!

[BeBuLamar]

Well the heater resistance does get lower but not by much. Perhaps a 9 ohms would be 8 ohms or so as the temperture difference between hot and cold is only a few hundred degrees.

[Kleinstein]

With normal heaters the diffeerence in resistance between hot and cold us usually small for 2 reasons:
1) they don't get that hot
2) they use alloys that don't chance the resistance very much to avoid the creation of hot spots. Ideally they even look for a slight negative TC so that the hotter parts gets lower resistance and thus less heat.

If even the 250 W heater causes toruble one should really check the wiring / connectors - this can well be a fire hazzard. Some drop in the light can be normal with the high power of the coffee maker though. In the US sometimes the wires are quite long and with the lower voltage the voltage drop gets more relevant.