Low Oil Pressure buzzer/alarm - SailNet Community
Reply
 
LinkBack Thread Tools
post #1 of 32 Old 04-14-2008 Thread Starter
Junior Member
 
Join Date: Nov 2007
Posts: 29
Thanks: 0
Thanked 0 Times in 0 Posts
Rep Power: 0
 
Low Oil Pressure buzzer/alarm

Hello,

I have a 1985 O'Day 28 with a Universal model 5411 diesel. The low oil pressure indication on this boat is only a small red light on the ingnition panel, which is almost impossible to see on a sunny day. In attempt to be proactive, I wire a radio-shack buzzer in parallel with the inidicator light, and voila! nothing. The light is definitely lit when I turn on the ignition key so I know there's power in the circuit coming from the low oil pressure switch on the block. Could it be that the voltage to the indicator light is much less than 12 volts and that's why the buzzer won't work? The buzzer that I bought is rated at 9-16 volts DC. Admitedly I'm no electrictian, but I checked the wiring schematic and it seems like all the wiring to the panel would be 12 volts. I tried the buzzer to an adjacent gauge and it worked fine. Any thoughts???
sapadeni is offline  
Quote Quick Reply Share with Facebook
Sponsored Links
Advertisement
 
post #2 of 32 Old 04-14-2008
Senior Member
 
Valiente's Avatar
 
Join Date: Jun 2006
Location: Toronto
Posts: 5,491
Thanks: 0
Thanked 0 Times in 0 Posts
Rep Power: 11
   
Get a voltmeter on the indicator light circuit or read the voltage off the light base itself (if it's incandescent as I suspect a 23 year old lamp would be).

Find out the output of the low oil pressure sensor, or (my choice) replace the sensor with a 12 VDC one, and then you can run the audible alarm in series with the lamp, or just get rid of the lamp, assuming you don't have deaf helmspeople.

Another possibility is that you've either wired the buzzer incorrectly or that the amperage is insufficient to activate the buzzer. Try it with the lamp OUT of the circuit.

Which makes me think...how do you create the conditions for oil pressure low enough to light the lamp in the first place?
Valiente is offline  
Quote Quick Reply Share with Facebook
post #3 of 32 Old 04-14-2008 Thread Starter
Junior Member
 
Join Date: Nov 2007
Posts: 29
Thanks: 0
Thanked 0 Times in 0 Posts
Rep Power: 0
 
The light is activated (circuit closed) by a pressure switch on the block. I just replaced the switch last weekend. Prior to that the light didn't work either. I would just rather have an audible alarm. Thanks for the advice.
sapadeni is offline  
Quote Quick Reply Share with Facebook
post #4 of 32 Old 04-14-2008
Senior Member
 
christyleigh's Avatar
 
Join Date: Dec 2001
Location: North Brookfield, Mass.
Posts: 935
Thanks: 0
Thanked 0 Times in 0 Posts
Rep Power: 14
 
Quote:
Originally Posted by Valiente View Post
Which makes me think...how do you create the conditions for oil pressure low enough to light the lamp in the first place?
Val, I'm assuming you were just having a brain fart because car, boat, whatever - Key ON engine not running equals OIL light on. If not fix it because it's broke.

Stan
'Christy Leigh'
NC 331
Wickford/Narragansett Bay RI
christyleigh is offline  
Quote Quick Reply Share with Facebook
post #5 of 32 Old 04-14-2008
Senior Member
 
Valiente's Avatar
 
Join Date: Jun 2006
Location: Toronto
Posts: 5,491
Thanks: 0
Thanked 0 Times in 0 Posts
Rep Power: 11
   
I don't have an oil light, just a pressure gauge. And I don't own a car...just a couple of boats...heh.

So the light goes OFF when the pressure's low? Or are you saying that the light blinks on at "ignition" and then goes off in a couple of seconds? Anyway, I don't have it.

Basically, when I switch the key to ON, only the panel indicator lights light. I then hit the glow plug button and then the starter button. I have no "kill cable", either, which I've seen. I simply turn the key, meaning it's just a solenoid like my propane system. If it were to break, I would stuff a rag in the air intake, I suppose, to kill the engine. Then I guess I could hotwire the starter if I couldn't get it fixed quickly.

I've seen the low pressure sensors on Atomic 4s, but a lot of A4 owners buy a four-buck "squealing pig alarm" from electronics supply stores. That's basically what I want to install on my diesel.
Valiente is offline  
Quote Quick Reply Share with Facebook
post #6 of 32 Old 04-14-2008 Thread Starter
Junior Member
 
Join Date: Nov 2007
Posts: 29
Thanks: 0
Thanked 0 Times in 0 Posts
Rep Power: 0
 
I'd be happy to use a "squealing pig alarm" if I can get it to work. Do you know how they wired it?
sapadeni is offline  
Quote Quick Reply Share with Facebook
post #7 of 32 Old 04-14-2008
Senior Member
 
christyleigh's Avatar
 
Join Date: Dec 2001
Location: North Brookfield, Mass.
Posts: 935
Thanks: 0
Thanked 0 Times in 0 Posts
Rep Power: 14
 
[quote=Valiente;299908]So the light goes OFF when the pressure's low? Or are you saying that the light blinks on at "ignition" and then goes off in a couple of seconds? Anyway, I don't have it.
Basically, when I switch the key to ON, only the panel indicator lights light. I then hit the glow plug button and then the starter button. I have no "kill cable", either, which I've seen. I simply turn the key, meaning it's just a solenoid like my propane system. End of quote.
No.... the light goes ON when the pressure is low - It's 0 psi with the key on and the engine not running. Yes... I have a 2 solenoid activated 'kill switches' on my NC also instead of a manual 'pull cable' as I had on other diesels.
I have the gauge, light, and buzzer that came with my boat in the pilothouse and I added a second Gauge (edit) and buzzer for the cockpit. To further answer your question the oil pressure drops considerably when the engine heats up as I'm sure you notice on your guage. The buzzer I installed for the cockpit is adjustable so I try to adjust it so it doesn't buzz at normal operating temps but when it drops below that certain psi it goes off - trouble is that sweet spot is hard to adjust with the little mini-pot on the guage so many times with a hot engine when I drop down to Idle ..... buzzzzzzzz. I could lower the setting waaaaay down but I want to know about the slightest drop in oil pressure..... so I put up with some false alarms.

Stan
'Christy Leigh'
NC 331
Wickford/Narragansett Bay RI

Last edited by christyleigh; 04-14-2008 at 02:43 PM.
christyleigh is offline  
Quote Quick Reply Share with Facebook
post #8 of 32 Old 04-14-2008
Midwest Puddle Pirate
 
US27inKS's Avatar
 
Join Date: Feb 2005
Location: Gardner, KS
Posts: 2,160
Thanks: 0
Thanked 0 Times in 0 Posts
Rep Power: 12
   
Sapadini.

Did you perhaps wire the alarm in series with the light instead of in parallel with it? If it's in series, the light will work but be a little dim and the alarm will not work. It does this because the current flow is limited by the item that uses the least current. That doesn't leave enough current to operate the buzzer. Wire them in parallel and the circuit will flow enough current for both devices, assuming that you have enough current available from the fuse and the switch will flow enough current for the ground.


To view links or images in signatures your post count must be 10 or greater. You currently have 0 posts.
John USYacht 27 "Cora Lee"
US27inKS is offline  
Quote Quick Reply Share with Facebook
post #9 of 32 Old 04-14-2008
Reward for lost Kraken!
 
hellosailor's Avatar
 
Join Date: Apr 2006
Posts: 11,445
Thanks: 5
Thanked 131 Times in 128 Posts
Rep Power: 11
   
Sapadeni-
I would guess that with the buzzer and bulb in parallel, what happens is that the bulb acts like a very low resistance (near zero ohms) so effectively it absorbs all the power and the buzzer gets none. If the bulb has a resistance of 1/2 ohm, and the buzzer is a maybe 600 ohms...the voltage divides proportionately and the buzzer won't sound.
The simplest most reliable solution will cost you about five bucks more. You disconnect the bulb, and replace it with an inexpensive 12-volt "dual pole" (DPDT or DPST, either will do) relay Wire up the relay coil to where the bulb was. The connect a 12-volt power lead to one side of both the relay's "NO" (normally open) contact pairs. Connect the blub to one of the paris, the buzzer to the other, and then connect them to ground. (If you buy a relay designed for car fog lights, there's usually a diagram included with it.)

The relay "goes on" instead of the originallight,and it isolates the light and buzzer so each one acts without interference from the other. That also will allow you to use a much more powerful buzzer.
hellosailor is offline  
Quote Quick Reply Share with Facebook
post #10 of 32 Old 04-14-2008
Midwest Puddle Pirate
 
US27inKS's Avatar
 
Join Date: Feb 2005
Location: Gardner, KS
Posts: 2,160
Thanks: 0
Thanked 0 Times in 0 Posts
Rep Power: 12
   
Quote:
Originally Posted by hellosailor View Post
Sapadeni-
I would guess that with the buzzer and bulb in parallel, what happens is that the bulb acts like a very low resistance (near zero ohms) so effectively it absorbs all the power and the buzzer gets none. If the bulb has a resistance of 1/2 ohm, and the buzzer is a maybe 600 ohms...the voltage divides proportionately and the buzzer won't sound.
The simplest most reliable solution will cost you about five bucks more. You disconnect the bulb, and replace it with an inexpensive 12-volt "dual pole" (DPDT or DPST, either will do) relay Wire up the relay coil to where the bulb was. The connect a 12-volt power lead to one side of both the relay's "NO" (normally open) contact pairs. Connect the blub to one of the paris, the buzzer to the other, and then connect them to ground. (If you buy a relay designed for car fog lights, there's usually a diagram included with it.)

The relay "goes on" instead of the originallight,and it isolates the light and buzzer so each one acts without interference from the other. That also will allow you to use a much more powerful buzzer.
While this explantion sounds good, it works a little differently. The current divides proportionally, not the voltage. With a parallel circuit, each leg of the circuit gets a full 12 volts and a full ground. Provided of course that the power supply and the ground are capable. The current on the circuit is increased by whatever the new item draws. In a series circuit, the total current flow is limited to whatever the lowest current flow item is, in this case the light bulb. While the light bulb's resistance is very low when read with an ohm meter, because of the inductive resistance of the filament when operating, the actual current flow is much lower than if it were just a resistor. You can prove this to yourself merely by applying ohms law to the 1/2 ohm light bulb. 12/.5 = 24amps in other words we would have a 288 watt warning light. In reality he likely has about a 3 watt bulb drawing .25 amps. A series circuit will only flow as much current as the LOWEST current user, in this case .25 amps. A quarter of an amp is not going to operate both the bulb and the buzzer, so the light comes on and the .25 amps passes through the buzzer to ground without sounding the buzzer.

I think that a relay would add unneeded complexity to it, unless the buzzer draws more amps than the switch will allow. If it does, he needs a new buzzer.


To view links or images in signatures your post count must be 10 or greater. You currently have 0 posts.
John USYacht 27 "Cora Lee"
US27inKS is offline  
Quote Quick Reply Share with Facebook
Reply

Quick Reply
Message:
Options

Register Now



In order to be able to post messages on the SailNet Community forums, you must first register.
Please enter your desired user name, your email address and other required details in the form below.
Please note: After entering 3 characters a list of Usernames already in use will appear and the list will disappear once a valid Username is entered.


User Name:
Password
Please enter a password for your user account. Note that passwords are case-sensitive.

Password:


Confirm Password:
Email Address
Please enter a valid email address for yourself.

Email Address:
OR

Log-in









Human Verification

In order to verify that you are a human and not a spam bot, please enter the answer into the following box below based on the instructions contained in the graphic.




Currently Active Users Viewing This Thread: 1 (0 members and 1 guests)
 
Thread Tools
Show Printable Version Show Printable Version
Email this Page Email this Page



Similar Threads
Thread Thread Starter Forum Replies Last Post
Oil Pressure Mystery Solved bsfree Gear & Maintenance 5 12-21-2007 07:23 PM
Breadmaker aboard CHRISTINE-R Provisioning 21 08-14-2006 11:43 PM
W60 - No oil pressure after oil change??? pma_foyl Gear & Maintenance 9 12-01-2004 09:45 AM
Changing Engine Oil Tom Wood Gear and Maintenance Articles 0 10-02-2002 08:00 PM
Oil Pressure Problems Tom Wood Gear and Maintenance Articles 0 05-16-2002 08:00 PM

Posting Rules  
You may post new threads
You may post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is On
Trackbacks are On
Pingbacks are On
Refbacks are On

 
For the best viewing experience please update your browser to Google Chrome