cncman40 Posted January 18, 2005 Report Share Posted January 18, 2005 Someone told me I could take a couple of resistors and a diode to reduce 12vdc to 6 volt dc....How can I do this???? Quote Link to comment Share on other sites More sharing options...
Guest Alun Posted January 18, 2005 Report Share Posted January 18, 2005 You need to be more specific, what do you want to power?If it's very low-power say <10mA then a zener diode would do.Higher power levels < 1.5A would need a regulator IC, eg. 7806, for even more power an external pass transistor would need to be added. Quote Link to comment Share on other sites More sharing options...
cncman40 Posted January 18, 2005 Author Report Share Posted January 18, 2005 Am looking for something I can use on my farm tractor to power the glow plugs....They cannot be run at full 12 volts dc. 6 volts is the max they can be run at..... Quote Link to comment Share on other sites More sharing options...
EnigmaOne Posted January 19, 2005 Report Share Posted January 19, 2005 You could run 2 - 6 Volt batteries in series, and tap the batteries to provide 6VDC for the glow plugs....or...If the proper connections are present on the glow plugs (two connection terminals on the glow plug itself, instead of an internally grounded terminal and a single external terminal), then run two in series. I'd imagine that you don't have an odd number of cylinders on that thing.Are you sure that tractor started out with a 12 Volt system? Most I've seen (of course it's been decades) were 6 volt system machines. Quote Link to comment Share on other sites More sharing options...
ante Posted January 19, 2005 Report Share Posted January 19, 2005 cncman40,So, now it Quote Link to comment Share on other sites More sharing options...
Guest Alun Posted January 19, 2005 Report Share Posted January 19, 2005 My mechanical knowledge is very poor - I don't know much about engines so may I ask a stupid question, what are glow plugs?If they're anything like spark plugs you need a high voltage in the order of about 10kV, not a low voltage. Quote Link to comment Share on other sites More sharing options...
jrcfg Posted January 19, 2005 Report Share Posted January 19, 2005 Alun:Glow plugs are simply "heaters"...they are used in diesel engines to provide the initial heat source (in each cylinder) to start combustion. Once the diesel engine is running, the glow plugs turn off as the heat of compression is enough to sustain combustion. (Diesels are relatively high compression engines). Quote Link to comment Share on other sites More sharing options...
Guest Alun Posted January 19, 2005 Report Share Posted January 19, 2005 Thanks for the info jrcfg,I agree with EnigmaOne, connect them in series if you can.Do they all have a common ground i.e. the tractor body or do they have separate +/- terminals, if they have a common ground a voltage regulator might be the only option.How much power do they use? - to me being heaters it sounds like they're pretty high powered so at 6V a linear regulator would have to dissipate half the power, so a switcher would be a good choice.Come to think of it if they're heaters then they would behave electrically as resistors, then you might be able to getaway with just pulsing them with 12V at 25% duty cycle to cause them to dissipate the same amount of power as if they were connected to 6V.Edit: 50% changed to 25% , I remembered Power = V^2/R! Quote Link to comment Share on other sites More sharing options...
ante Posted January 19, 2005 Report Share Posted January 19, 2005 On a 12Volt system they can draw up to 90A when cold. Quote Link to comment Share on other sites More sharing options...
EnigmaOne Posted January 19, 2005 Report Share Posted January 19, 2005 That settles it. Use 4 - 'D' cells. In series. ;D Quote Link to comment Share on other sites More sharing options...
ante Posted January 19, 2005 Report Share Posted January 19, 2005 Yes, high current NiCd D cells would probably work. 8) Quote Link to comment Share on other sites More sharing options...
Dazza Posted January 19, 2005 Report Share Posted January 19, 2005 Hi,Why not use a resistor on each glow plug to drop the voltage, then use a timer circuit to supply power to the glow plugs via relays, you only need around 5 to 10 seconds depending on your climate. The resistor will only need to withstand the current being drawn through them for that short period of time. Someone else will have to provide the answer for the resistors values and wattage needed, (1) pushbutton to start timer, LED comes on.(2) LED turns off start engine.(3) time to get back to work. ;D ;D Quote Link to comment Share on other sites More sharing options...
ante Posted January 21, 2005 Report Share Posted January 21, 2005 Hi Dazza,The heat is needed inside the combustion chamber, with resistors half the heat will be on the outside! ;D ;D ;D Quote Link to comment Share on other sites More sharing options...
Dazza Posted January 22, 2005 Report Share Posted January 22, 2005 Hi Ante,Yes that's right, this is for warming up your hands on those cold winter mornings ;D ;D ;D.The right wattage resistor should handle the heat for this short period of time?Maybe two 10 watt resistors for each glow plug, then mount them to a basic heat sink, a small sheet of aluminium plate. Quote Link to comment Share on other sites More sharing options...
ante Posted January 23, 2005 Report Share Posted January 23, 2005 Hi Dazza,Yes it would work, the easy way would be to use one extra glowplug in series with each as a resistors. A glowplug have a dynamic resistance (it changes with temperature) and is not easy to make a good voltage divider with a conventional resistor. The extra plugs can be fitted under the seat for cold winter days. ;D Quote Link to comment Share on other sites More sharing options...
Dazza Posted January 23, 2005 Report Share Posted January 23, 2005 Hi Ante,Oh well, I at least try to help ;D Quote Link to comment Share on other sites More sharing options...
ante Posted January 24, 2005 Report Share Posted January 24, 2005 Dazza,Yes, of curse! I would be much easier if the plugs where isolated and had two connections each. But I haven Quote Link to comment Share on other sites More sharing options...
Recommended Posts
Join the conversation
You can post now and register later. If you have an account, sign in now to post with your account.