Remote starter button wiring

[Webb]

Would somebody mind proofing my diagram please.

Some explanation to prevent confusion.

In addition to the standard panel start momentary switch, I want a remote start button using the index button on the stick so I can start on the ground without holding the stick back with my knees.

The panel button is always hot. The stick start button can be turned off by a toggle switch so it can’t accidentally be pushed when flying. Also there is a LED annunciator to let me know if I forget to turn the stick switch off.

The wiring size for the grip requires a relay to activate the starter solenoid. The stick switch goes to ground so the power to activate the relay comes from the starter 12V+.

Thanks in advance.

 

[Freemasm]

Probably not understanding your intent, but:

Why wouldn't the SS-off be the first switch from the A+ and called a "start enable"? Part of your circuit always being hot has its potential safety issues.

Switching on the ground circuit of a relay has benefits for circuit/bus control: no wire protection device and a "fail-op" mode. On the starter, fail-op means a potential, un-commanded starter engagement. Potentially dangerous and expensive.

Let me know if I'm not following. Some of talented electrical guys will certainly chime in here.

 

[rocketman1988]

Typically

Yes, typically the starter contactor coil is powered by the switch for the reasons stated. A Master contactor (continuous duty) has the coil switched to ground.

 

[Webb]

Probably not understanding your intent, but:

Why wouldn't the SS-off be the first switch from the A+ and called a "start enable"? Part of your circuit always being hot has its potential safety issues.

Switching on the ground circuit of a relay has benefits for circuit/bus control: no wire protection device and a "fail-op" mode. On the starter, fail-op means a potential, un-commanded starter engagement. Potentially dangerous and expensive.

Let me know if I'm not following. Some of talented electrical guys will certainly chime in here.

Perhaps always hot is not a correct way to state it. The panel start button is wired normally.

The Toston stick switch goes to ground so power has to come from the relay to the stick instead of from the stick to the relay.

A relay is required because the wire gauge in the grip switch is too small to handle the current.

I’m asking for the talented wire guys to review since a second start button is unusual as well as annunciation to alert the second start button is enabled.

 

[Freemasm]

Perhaps always hot is not a correct way to state it. The panel start button is wired normally.

The Toston stick switch goes to ground so power has to come from the relay to the stick instead of from the stick to the relay.

A relay is required because the wire gauge in the grip switch is too small to handle the current.

I’m asking for the talented wire guys to review since a second start button is unusual as well as annunciation to alert the second start button is enabled.

Please re-read my reply. It is a sincere attempt to help you safely attain your intent as I understand it. I would understand your defense of the approach if it were misunderstood. That does not appear to be the case. You asked for feedback.

A single action (single push button) starter engagement is dangerous. Moving one switch in conjunction with the following remedies that if I understand your circuit.

I understand the need for a relay. It is my strong opinion, FWIW, that the related contact is not as safely controlled as it should be per the reasons stated.

In most cases, I would say "your build" but your proposed configuration could place others at risk.

Build safe, Sir

 

[Webb]

Please re-read my reply. It is a sincere attempt to help you safely attain your intent as I understand it. I would understand your defense of the approach if it were misunderstood. That does not appear to be the case. You asked for feedback.

A single action (single push button) starter engagement is dangerous. Moving one switch in conjunction with the following remedies that if I understand your circuit.

I understand the need for a relay. It is my strong opinion, FWIW, that the related contact is not as safely controlled as it should be per the reasons stated.

In most cases, I would say "your build" but your proposed configuration could place others at risk.

Build safe, Sir

Thank you for the input. As I looked at the drawing, the cut off switch needs to be moved to the input to the relay which completely shuts down the remote circuit if I understand what you are saying.

Moving the disable switch kills the entire remote start circuit. Even though the button on the stick is recessed, that’s why there is a kill switch after ground starting with annunciation when it’s active. I don’t want the chance to hit it by accident when flying. That circuit will only be active during starting procedures on the ground. Otherwise the panel button can be used instead.

The single action push button on the panel is a guarded button that is used for starter buttons. It’s the one Stein sells.

You helped me realize my first draft did not properly disable the remote circuit. Thank you.

 

[Freemasm]

Even in that case, there is still a single action start button on the panel. There is unnecessary risk there. Moving it the first component in your diagram adds safety.

The failure mode on the added relay for a short will is fail-op -> the starter will energize "uncommanded" once the enable switch is closed. Not ideal.

Since this is a retrofit, I'll throw out a different approach. I don't know your current configuration; however, it could be a little more work and potentially quite a bit less than you are proposing. It either case, it is safer and will have better reliability IMO (less components).

See attached. Replace the starter relay with one that utilizes a PWM'd coil (GigaVac, Blue Sea, etc). This will bring the related control circuitry current down into the mA range which is the intent of the extra relay approach you are proposing. The (single) relay circuit controlled on the hot side, not ground for aforementioned safety reasons.

Want even a little simpler? Consider combining the "Start Enable" and "Start (panel)" switches into a single, quality (Honeywell TL or similar) progressive off-on-(on)

Just a (simple) option. If I'm wrong, people will tell me here and Carl Froelich will call to tell me what a dumba$$ I am.

Build safe, Sir.

 

[vlittle]

I only have a stick button for the starter. It is enable when the Master switch is ON and disabled when the Master switch is ALT. There is no separate enable switch or light required, just one relay. You can easily add a panel switch.

http://www.vx-aviation.com/sprocket/photos/panel_elec/schematics-2/MASTER.pdf

 

[Webb]

Even in that case, there is still a single action start button on the panel. There is unnecessary risk there. Moving it the first component in your diagram adds safety.

The failure mode on the added relay for a short will is fail-op -> the starter will energize "uncommanded" once the enable switch is closed. Not ideal.

Since this is a retrofit, I'll throw out a different approach. I don't know your current configuration; however, it could be a little more work and potentially quite a bit less than you are proposing. It either case, it is safer and will have better reliability IMO (less components).

See attached. Replace the starter relay with one that utilizes a PWM'd coil (GigaVac, Blue Sea, etc). This will bring the related control circuitry current down into the mA range which is the intent of the extra relay approach you are proposing. The (single) relay circuit controlled on the hot side, not ground for aforementioned safety reasons.

Want even a little simpler? Consider combining the "Start Enable" and "Start (panel)" switches into a single, quality (Honeywell TL or similar) progressive off-on-(on)

Just a (simple) option. If I'm wrong, people will tell me here and Carl Froelich will call to tell me what a dumba$$ I am.

Build safe, Sir.

Thanks Scott. I think we are on a very similar track. I still have to have a relay for the stick due to the wiring gauge.

I appreciate the safety concerns you brought up.

 

[Freemasm]

I'm all about combining functions when it makes sense, like your (vlittle's) example . It provides the functionally of the start enable. Very nice. The main point is, the likelihood of an accidental starter engagement is reduced/safety increased for you.

The OP wants/needs to have a low current flow to his start-stick button. An old style start relay will need the added relay or switch to a low current coil start relay. Combining the approaches could save the OP time, money, and valuable panel/command center space.

 

[Freemasm]

Thanks Scott. I think we are on a very similar track. I still have to have a relay for the stick due to the wiring gauge.

I appreciate the safety concerns you brought up.

The PWM type start relay only draws about 150mA, If your current wiring/button rating will draw the proposed relay, it will most certainly power the replacement I proposed. Just another option for you.

Sorry to keep on this but I'm continuing to layout my system architecture. This is on my brain a lot. My current plan is to have my PTS on the end of my throttle handle. Yes it will need an enable/disable functionality but hopefully it will allow one hand on throttle, other on stick like you're gunning for. I like vlittles start enable approach and may incorporate it; another useful and creative thing you can learn here.

 

[Freemasm]

The LED in your circuit (I assume that "sun like" symbol is an LED) will only illuminate when the start switch is engaged.

Also, don't forget that LED's are diodes and need/require a current limiting circuit (resistor) to keep from melting the wire.

Yes Sir, just trying to show the component location relative to the OP's proposed one on a quick white board sketch. Thanks for catching my incompleteness.

I already don't sleep like a normal person and this stuff bumping around in my numb skull doesn't help.

 

[bjdecker]

Yes Sir, just trying to show the component location relative to the OP's proposed one on a quick white board sketch. Thanks for catching my incompleteness.

I already don't sleep like a normal person and this stuff bumping around in my numb skull doesn't help.

Insomnia + VAF ==> More Insomnia

and I should have said if it's a 12V circuit, use a 12V capable LED (forward voltage), otherwise bright flash occurs and LED fails...

 

[Ruready]

Piper made the PA20 and 22 with a start button wired directly to the battery, its under the seat so it cannot accidently be pushed, no start solenoid just the heavy duty start button, its always hot and starts with the battery master OFF. Works great

 

[Webb]

Tested the circuit out after dinner tonight. It worked as designed.

LED on circuit enabled. Off when disabled.

Solenoid for starter activated correctly for panel and stick switches. Switch relay for stick worked.

A happy camper.

 

[Webb]

Thanks for the help guys. Everything worked according to plan.
Here is a cleaned up diagram. The stick switch is drawn incorrectly and is a momentary button but you get the idea.

Also not shown is a 20K resistor to tone down the brightness of the LED. Two identical LEDs on that side of the panel and this LED was about 5 times as bright.

 

[Snowflake]

Building on Vern's suggestion:

1. Why keep the panel start button at all? If you have to hold the stick back anyway, when would you want to use a panel button?

2. If you do have a panel button, why not just wire it in parallel with the stick switch? That way the enable switch/enabled light is illuminated when the starter is active, and reminds you to deactivate after start... Accidentally pushing the panel start button when you didn't intend to is also a thing.

 

[Desert Rat]

I did pretty much the same thing that Webb is doing.

You need both hands to start a fuel injected Lycoming. You need to hold the stick back during start in a tailwheel airplane. I wanted a way to start a fuel injected engine in a tail wheel airplane without having to hold the stick back with my knees or grow a third arm.

Note that I said want, not need. So, in designing this I reasoned that the stick start circuit was an additional convenience feature not a replacement for a conventional starting circuit.

My criteria was that it must be guarded against against accidental activation, and since it has more components to fail, shouldn't be able to leave me stranded if say for example, the relay or stick button failed.

Based on these criteria, my stick start is only active when armed by a guarded switch on the panel that also throws a CAS message on the PFD. The conventional panel start button (it's the flush one that Stein sells where you have to intentionally push it in deeper than the face of the panel to get it to engage) is active any time the master is on.

For those who have commented that an always hot push button on the panel is unsafe due to the potential for an accidental poke, I get the concept, but it's a common design in lots of certificated airplanes. Pipers and most prop twins come to mind.

 

[Webb]

Building on Vern's suggestion:

1. Why keep the panel start button at all? If you have to hold the stick back anyway, when would you want to use a panel button?

2. If you do have a panel button, why not just wire it in parallel with the stick switch? That way the enable switch/enabled light is illuminated when the starter is active, and reminds you to deactivate after start... Accidentally pushing the panel start button when you didn't intend to is also a thing.

1. Several reasons. First was I wanted it followed by others.

2. The Tosten stick switch needs a relay since the circuit closes to ground when the stick button is pushed. The light is on when the circuit is enabled.

I suspect the concerns about accidentally pushing the panel button comes from those with keyed switches. Panel start buttons typically are guarded and accidental activation is just about zero. I’ve got to stick my finger in a hole to push the button.

IMHO, a panel start button is safer than a key start because it requires separate mag switches. When doing a mag check with a key, there is a possibility of going beyond run to the start position.

 

[Mich48041]

Attached is a circuit with a hidden start enable switch.