Over the weekend I ran a test on an old OHP to see if I could do anything about the heat.The OHP has a built in fan which gets rid of most of the heat but when you switch the OHP off the fan also goes off.We all know that a bulb does not cool instantly when turned off,which means that there is still heat in the OHP that can damage the Fresnel or things you have put in.My solution was to place a small timer circuit In the OHP connected to the fan so that when the Main OHP switch was turned off it would turn the circuit on for about 5mins letting air circulate throughout the OHP getting rid of the excess heat.It worked very well and I am now perfecting the circuit by putting a temperature switch in to turn off the fan when it hits a targated temprature.
This circuit will work on any OHP or home made projector.
If anyone is interseted I will post more info.
This circuit will work on any OHP or home made projector.
If anyone is interseted I will post more info.
Russell,
Since I just found out how to wire my fan up about 5 minutes ago, I'm also interested in how to get it to run automatically after i've shut the light off until the temperature hits a certain level. I'm interested in how your timer circuit works (what parts are needed.. I don't know much about this circuit stuff).. and also your plans for the temperature shutoff.. if its not too much to ask. 🙄
Is it essentially using a timer as a "switch"? Please post more about your setup, it sounds really useful to know 🙂
Thanks in advance,
-rep
Since I just found out how to wire my fan up about 5 minutes ago, I'm also interested in how to get it to run automatically after i've shut the light off until the temperature hits a certain level. I'm interested in how your timer circuit works (what parts are needed.. I don't know much about this circuit stuff).. and also your plans for the temperature shutoff.. if its not too much to ask. 🙄
Is it essentially using a timer as a "switch"? Please post more about your setup, it sounds really useful to know 🙂
Thanks in advance,
-rep
At the moment I am perfecting the circuit to take 120-240volts.It will also be compatable with 12volts and anything higher or lower.It is a very simple circuit consisting of a 555timer and a few resistors which I will list when I get it working properly.If you search the web you will find alot of circuits that use the 555timer,I have just modified one to suit my needs.I will have to go to the local electronics store to get more parts to finish it.I will send a diagram of the timer circuit when it is finished.I will start the temperature senser when I have finished timer circuit.
Sadd3j
I was wondering what sort of voltage your fan takes.
I'll try and get the diagram done tonight so I can post it tomorrow.
Thanks for your interest
Sadd3j
I was wondering what sort of voltage your fan takes.
I'll try and get the diagram done tonight so I can post it tomorrow.
Thanks for your interest
On my OHP it has a bulb changer, with in one socket it has a working bulb and in the other it has nothing. So when I turn my OHP off, I just slide the bulb changer and turn the OHP on again, so the fan goes, but as there is no bulb there is not light = no heat 🙂
Im sorry that I have not posted the diagram or any info in a few days.My computer has died on me again.It still works but not in the way I would like it to.I have sent it in and should get it back on monday.At the moment I am writing from the internet Café,I had to send off some e-mails and so thought I should read any new posts.Ill send a message when my pc's back.
Hmm, sorry I didn't reply.. for some reason I didn't see when anyone posted in this thread?? 
Anyway, I'm still unsure about my OHP cooling yet. I have one big AC 120v fan.. and then I was planning on maybe 1 DC fan to suck air out of the main OHP and then maybe 2 DC fans up around the LCD to remove heat. I'm still waiting on some parts so I don't even have a basic projector going yet.
Anyway, keep me (and the forum) informed!
-rep
Anyway, I'm still unsure about my OHP cooling yet. I have one big AC 120v fan.. and then I was planning on maybe 1 DC fan to suck air out of the main OHP and then maybe 2 DC fans up around the LCD to remove heat. I'm still waiting on some parts so I don't even have a basic projector going yet.
Anyway, keep me (and the forum) informed!
-rep
It has been long time since I visited DIY
I had a problem with the immense heat generated from the OHP. When I put an LCD on top of the OHP, in a few minutes the center of the LCD showed growing circular dark spots. Initially I was hirrified thinking i might have damaged the LCD.
What i did was put a $14 fan bought from walmart on the side of OHP. With the fan blowing in full speed, i did not see any spot anymore.
I have been using this solution for 8 months now - with no overheating problem.
I had a problem with the immense heat generated from the OHP. When I put an LCD on top of the OHP, in a few minutes the center of the LCD showed growing circular dark spots. Initially I was hirrified thinking i might have damaged the LCD.
What i did was put a $14 fan bought from walmart on the side of OHP. With the fan blowing in full speed, i did not see any spot anymore.
I have been using this solution for 8 months now - with no overheating problem.
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