555 timer circuit help

[budm]

Re: 555 timer circuit help

I think that is all getting too involved. Here is a pic if the commercially available product. I see a timer, regulator, microcontroller, and a transistor. I dont think there is anything on the other side. I dont need the microcontroller. The the top right is the input and the left is the output. the other lead coming off that is the push button with a LED inside it. (My guess is black is ground, red is the switch, and yellow is the LED. I assume that large component is a 1.5 resistor?

I think without the microprocessor the footprint of this could be reduced. I dont need over protection, resistance across the filament, and 10 different ways of programming it. Just on for 10 seconds with a condition indicator.

I might just buy one and reverse engineer the microprocessor out of it.

Basically I want this without the microprocessor, and the lead with the button, and having two LEDs and button on the board.

I was thinking maybe a mosfet to trigger the glow plug and the opamp for the LEDs?

So what is the sup[ply Voltage for that board? 5V? And the output Voltage to the plug is???? And the price for that board is???
It has 5V regulator on the board so input must be higher than 5V, but you said you need 1.5V 3A for the plug, so how is that board being used for?
If you look real close, the output is connected to an inductor, and the other side is connected to that large IC big trace to handle large current, I have never seen micro controller that can output large current like that, the GND trace for that IC is also big, so more likely to be some kind of power switching device because as you can see there is no relay to supply the power to the plug.
What is the specification of that board? I would find out before buying so you will have some idea what can be done to it since you have low budget.

[eccerr0r]

Re: 555 timer circuit help

The "commercial" product is probably checking the heater when it's off, something that can be easily done with a microcontroller without you noticing it.

In fact it looks like the "microcontroller" is doing the switching directly. That can't be a generic part it looks, no idea what part number that microcontroller is?

[garry7263]

Re: 555 timer circuit help

I think that is all getting too involved. Here is a pic if the commercially available product. I see a timer, regulator, microcontroller, and a transistor. I dont think there is anything on the other side. I dont need the microcontroller. The the top right is the input and the left is the output. the other lead coming off that is the push button with a LED inside it. (My guess is black is ground, red is the switch, and yellow is the LED. I assume that large component is a 1.5 resistor?

I think without the microprocessor the footprint of this could be reduced. I dont need over protection, resistance across the filament, and 10 different ways of programming it. Just on for 10 seconds with a condition indicator.

I might just buy one and reverse engineer the microprocessor out of it.

Basically I want this without the microprocessor, and the lead with the button, and having two LEDs and button on the board.

I was thinking maybe a mosfet to trigger the glow plug and the opamp for the LEDs?

[jiroy]

Re: 555 timer circuit help

The 555 is a pretty powerful chip but cannot handle 3 amps. IIRC it has a maximum output of about 200mA, and I don't think it can pass that at 5 volts.

Plus you have that LED in series which means 3 amps must pass through that due to KCL. You'll need a relay or transistor to pass that much current.

How are you detecting the filament failure? Should the filament failure LED be on, even when the button isn't pressed?

A schematic would be helpful.

Same thought jumping to my head , A relay is needed ...

[budm]

Re: 555 timer circuit help

10 watts for 10 seconds = 100 watt-seconds = 1.67 watt-minute = 28mWh of power... Might be OK to waste it, might not, dunno.

So, do we want to PWM the 5V to the glow plug?

Why not? If it meets his requirement, his budget. One more 555 or dual 555, caps, resistors, trim pot, power MOSFET, heatsink, etc.

[eccerr0r]

Re: 555 timer circuit help

10 watts for 10 seconds = 100 watt-seconds = 1.67 watt-minute = 28mWh of power... Might be OK to waste it, might not, dunno.

So, do we want to PWM the 5V to the glow plug?

[budm]

Re: 555 timer circuit help

The battery I use for the flight pack is a 7.2 Li-Po battery using a switching BEC to put out 5 volts. They are 45c batteries are capable of pulling about 80 amps current and hold 2200mah. Cant drain the batteries below 3.2 volts though without damaging them. I have been flying with this set up for a long time and only have to recharge once a week. I use Li-Po battery of the same capacity in my transmitter. Saves a lot of charging time.

Well as I already indicated, you will be wasting 10W of power for what ever how long the plug stays on, if that is not a concerned to you, then use the linear regulator with BIG heatsink to dissipate the heat from the regulator so it does not burn up, so more weight due to added heatsink and that is an added cost to your BOM.
Designing a product is full of compromised, it is a matter of what is acceptable to you or your customer.

[garry7263]

Re: 555 timer circuit help

The battery I use for the flight pack is a 7.2 Li-Po battery using a switching BEC to put out 5 volts. They are 45c batteries are capable of pulling about 80 amps current and hold 2200mah. Cant drain the batteries below 3.2 volts though without damaging them. I have been flying with this set up for a long time and only have to recharge once a week. I use Li-Po battery of the same capacity in my transmitter. Saves a lot of charging time.

[budm]

Re: 555 timer circuit help

Well, it is another requirement that should be on the list.
So how are you going to solve the power problem if all you have is the 5V power supply, that is your big problem, you do not want to waste power, do you?

[garry7263]

Re: 555 timer circuit help

Meaning that when you power the circuit on by pressing the momentary switch, it automatically drops the voltage to pin 2 to turn the timer event on, then when the even plays out, it cuts its own voltage to the relay and shuts off completely.

[garry7263]

Re: 555 timer circuit help

The timer wont draw that much current when it is not activated. Maybe it is possible to use a momentary switch to activate a relay that will supply current for the 10 seconds, then when the timer goes out, it cuts power completely to the circuit?

[budm]

Re: 555 timer circuit help

Well, if the plug is open then there will be no Plug OK indicator (Green LED), so the plug is not going to draw the current but the relays and the timer will be drawing the current, and when the replay is off after 10 seconds, the timer will still be drawing current which your Green LED is not going to show you that because you do not have any current sensing device to see if there is current being drawn from the battery, so another added circuit.

[eccerr0r]

Re: 555 timer circuit help

Dang, you should have said heater from the get go, then it would give a good reason why you can't see the heating element.

Also this is a heater and you probably don't care that much about the exact voltage so some drop is OK. Also a relay is not necessary, a logic level MOSFET will also work if not better and smaller than a relay.

[garry7263]

Re: 555 timer circuit help

Also, the idea behind the indicator LEDs are to let me know when the device is putting a drain on the battery weather the plug is bad or not. On the cheap Chinese one, (in the pics) you can see there is not much there, and that has the ability to be activated with the transmitter. So I am just interested in losing the remote button/LED and opting for two LEDs on the end with a tactic momentary switch, and losing the transmitter control circuit.

The programmable one is just way to large and heavy. I have one like the Sullivan one for an OS FT1.60 twin, but that too is too much for what I need for a heli, but on a 1/4 sized CUB, that wont even notice the weight.

[budm]

Re: 555 timer circuit help

Well you are going to solve power problem which I already explained.
Do you mean you cannot spend about $10 for those two modules on Ebay? If that is the case I do have cheaper solution for you.
Just added up all your parts and see how much it will cost.

[garry7263]

Re: 555 timer circuit help

This is actually what I am trying to make. But I am too broke, and cheap to spend that. Plus I want to try to build my own. Many of the onboard glow circuits go for $25-$100. My needs are more simple. I just want to push the button to turn it on and have it be on for 10 sec at a time to reduce the possibility of burning out the glow plug and not drain the battery, and just to have an indicator to know if the plug got burnt.

These other circuits have the ability to turn them off and on from your transmitter, or to have them operate at low throttle when you are dumping more fuel in the carbs that sometimes chokes them out and stalls them. I have one of those for a twin cylinder motor I have, but for the helicopters I have, I just need a simple circuit and have it with the smallest footprint and lightest weight possible.

Here is one of the cheaper ones:
Cheap Chinese Glow Driver

The larger and more elaborate one:
Sullivan Onboard Glow Driver

Or this one:
Programmable Onboard Glow Driver

Basically the only change in the Chinese one is that I don't need to be able to operate it from my transmitter and I want an indicator to show that it is on and working or that there is a problem with the plug. I was thinking I could integrate the button on the PCB, and have the two LEDs at the end so when covered with clear shrink tubing, it would be easily visible. It will be going on helicopters so having the end of the PCB hanging from the edge of the canopy is not a problem.

[budm]

Re: 555 timer circuit help

Think what you need to consider when building the circuit: you write thins down one by one and see how to accomplish each requirement.

1) 5V power source and the load requires 1.5V @ 3A, so the Voltage regulator will have 5V - 1.5V = 3.5 V drops on the regulator, so power dissipation for the 1.5V regulator will be 3.5V X 3A = 10.50 Watts of wasted power. If your power source is battery then you are just wasting lots of power for nothing, any device in series with the load will have dissipate that power to drop 5V down to 1.5V.
You should look into something like this:
http://www.ebay.com/itm/5A-power-75W...item4621fc2b7d

2) You already have Green LED indicator that will show you if the filament, wiring, regulator are OK or not, if the filament is bad then the LED will not light up, so just label the LED as 'Filament OK' indicator, if it does not light up when you press the start button to start the timer then you know you MAY have problem with the filament, the wiring to the filament, or bad 1.5V regulator. Why would you need the Red LED to tell you if the filament is bad.

Timer module:
http://www.ebay.com/itm/DC-5V-12V-Ad...item1c6a3ddb70

[eccerr0r]

Re: 555 timer circuit help

-It's not "half" it's one... the IC has two in it.
-It's not strictly necessary to put a cap on the control voltage pin of the 555
-KiCad didn't have a SPST relay, only a DPDT, so you get the picture...
-Look very carefully how the power is connected, yours is connected wrong.
-R8 is just there to prevent killing the LM358's output. Its value isn't very critical.

I changed it a bit, I always end up cheapening the circuit ... why do I do it I don't know... Maybe...

[garry7263]

Re: 555 timer circuit help

I redrew it more or less to figure out the current flow.

-Only using half the op-amp? It is 3 volts in total I assume.
-I noticed the cap from pin 5 to ground.
-I am guessing that K1 is a dual relay.
-I put in the 1.5v regulator as I assume that the 1.5 volts was a separate power source. Maybe put a diode inline to keep flow back to the rest of the circuit?
-The bulb pulling current along with the resistor R8 restricts the threshold to the transistor?

[eccerr0r]

Re: 555 timer circuit help

No guarantees but this has the general concepts that should do what you want from the initial design requirements.

Note that it is still not using the bulb (R3) as the sense item, it requires an external sense R4, and yes it's only 0.047 ohms.