BRINDUS44 Posted June 10, 2020 Report Share Posted June 10, 2020 Hi Electrickery Wizards, possibly a numpty question, but my original TR6 heater motor has a green tubular object ( a resistor?) in the wiring circuit which I guess is to enable 2 speeds - would this not work with the SPAL motor too? Thanks Ian Quote Link to post Share on other sites
RobH Posted June 10, 2020 Report Share Posted June 10, 2020 Yes of course it would work Ian - it is the simplest solution but will only give one fixed slower speed. The pulse-width-modulation units being tried out by Andy and Roger should give continuously variable speeds and don't get anything like as hot as your green wire-wound resistor will. (though maybe in a heater that is no bad thing?) Whether you consider the extra complication to be necessary is a purely personal choice. Quote Link to post Share on other sites
RogerH Posted June 10, 2020 Report Share Posted June 10, 2020 Hi Ian, you are quite right. The resistor would drop a few volts and thus the speed would reduce. What we are trying to do by replacing the fan with a more modern design is to give it a bit more puff to help clear the screen etc. A second speed isn't really that necessary as plenty of air comes in when driving forwards. But hey !! it can be done. Don;t touch that green tubular object when it is running because it could get quite hot. In fact the person that did that mod was quite clever and has put the resistor in the air stream to keep it cool. Roger Quote Link to post Share on other sites
BRINDUS44 Posted June 10, 2020 Report Share Posted June 10, 2020 Thanks for the clarification guys - I await the final outcome ! Quote Link to post Share on other sites
RogerH Posted June 11, 2020 Report Share Posted June 11, 2020 (edited) Badgers nadgers !!! I have found more about what is going on. The 4A two speed wiper motor switch can switch two speeds. Pin 4 is common +12V Pin 6 or 7 could be for fast Pin 8 could be for slow. What I have also found is the the controller module power earth must not be connected to the Motor output earth I tried various combinations of wiring also using a Normally Open relay all to no avail. I'll have another go tomorrow as I would like to use the controller. Perhaps a common _ve and a switched earth !!!! Roger Edited June 11, 2020 by RogerH Quote Link to post Share on other sites
Lebro Posted June 11, 2020 Report Share Posted June 11, 2020 https://www.youtube.com/watch?v=Ek0Q8qfjx_Y&feature=youtu.be This is a video showing the waveform present on a 27W bulb at 12Volts (drawing around 3 Amps) It clearly shows that when "flat out" the output is fully on, & there is negligable volts drop. The photo shows to volts drop across the speed controller when fully on = 30 mV which would not slow the heatre motor to any extent. If you say the new motor you are using draws 4 Amps, then one could assume the voltage drop would be in proportion so 40 mA. Bob Quote Link to post Share on other sites
RogerH Posted June 11, 2020 Report Share Posted June 11, 2020 Hi Bob, Using a 12V battery (engine not running) there is a noticeable audible difference between car 12V and controller full power. So there is a little drop. With the engine running the difference may be smaller as there are a couple more volts coming through. I have found with the controller, that I have, it does not like the power earth and motor earth being connected. So I have now come up with a simple circuit whereby the earth is switched (as per the DR3 motor). I'll try this tomorrow. Roger Quote Link to post Share on other sites
RobH Posted June 11, 2020 Report Share Posted June 11, 2020 Excellent video Bob. Nice demonstration of PWM. Perhaps the difference between what you are seeing and what Roger observes is that you are using a resistive load while the motor is an inductive load which will generate switching noise from the commutator? A bit of capacitive smoothing may work wonders. Quote Link to post Share on other sites
Lebro Posted June 11, 2020 Report Share Posted June 11, 2020 (edited) I am also using a different controller, as the one Roger has was out of stock. I went for this one: https://www.ebay.co.uk/itm/12V-24V-Max-20A-PWM-DC-Motor-Stepless-Variable-Speed-Controller-9V-60V/353043539527?ssPageName=STRK%3AMEBIDX%3AIT&_trksid=p2060353.m2749.l2649 I will be trying it on my standard TR3 heater as soon as I get a chance. Bob Edited June 11, 2020 by Lebro Quote Link to post Share on other sites
AndyR100 Posted June 11, 2020 Author Report Share Posted June 11, 2020 2 hours ago, Lebro said: https://www.youtube.com/watch?v=Ek0Q8qfjx_Y&feature=youtu.be This is a video showing the waveform present on a 27W bulb at 12Volts (drawing around 3 Amps) It clearly shows that when "flat out" the output is fully on, & there is negligable volts drop. The photo shows to volts drop across the speed controller when fully on = 30 mV which would not slow the heatre motor to any extent. If you say the new motor you are using draws 4 Amps, then one could assume the voltage drop would be in proportion so 40 mA. Bob Hi Bob, thanks for taking the time to hook up your controller, it certainly appears to be well-behaved - looks to be a good choice. Will await the outcome of Rogers wiring/switch re-jig and then have another play with my set-up. ...... Andy Quote Link to post Share on other sites
RogerH Posted June 11, 2020 Report Share Posted June 11, 2020 (edited) Hi Andy, I believe this circuit will overcome the oddity with the common earth connections. The switch is a 4A DR3 two speed wiper motor switch - any switch would do. I will give it a go first thing in the morning. Roger Edited June 12, 2020 by RogerH Quote Link to post Share on other sites
AndyR100 Posted June 11, 2020 Author Report Share Posted June 11, 2020 11 minutes ago, RogerH said: Hi Andy, I believe this circuit will overcome the oddity with the common earth connections. The switch is a 4A DR3 two speed wiper motor switch - any switch would do. I will give it a go first thing in the morning. Roger Hi Roger, thanks for confirming the set-up..... fingers crossed for success! ....... Andy Quote Link to post Share on other sites
Andy Moltu Posted June 12, 2020 Report Share Posted June 12, 2020 Thanks for that. Was trying to figure the same out but as the switch hadn't arrived I couldn't work out the connections. Does that mean that the PWM effectively regulates the power via the earth/-ve connection to the motor? As the wiring diagrma effectively means the motor gets a full 12v +ve feed all the time. If not the switch might need to be connected to the live +12v feed and use a changeover relay to divert the motor directly to earth when using full power. Quote Link to post Share on other sites
RogerH Posted June 12, 2020 Report Share Posted June 12, 2020 Hi AndyM, the fan and controller are connected to a permanent +12V (as per the TR4/4A two speed wiper motor DR3). The switch moves the earth around. So looking at the circuit diagram above - 1 -The first switch position connects the fan earth to earth and runs at full power. 2 - the second position moves the earth to the Controller earth 'power input' and disconnects the fan from the car body earth. Hopefully the earths will not interact with each other. The switched earths can be swapped over so that slow can come on first if you wish. Roger Quote Link to post Share on other sites
Lebro Posted June 12, 2020 Report Share Posted June 12, 2020 It is normal for dc switching controllers to switch the -VE line. P channel mosfet generally cheaper, & lower on resistance. Bob Quote Link to post Share on other sites
Andy Moltu Posted June 12, 2020 Report Share Posted June 12, 2020 Thanks for education me on the earth (-ve) line normally being swiched - which is good in that it makes the switch wiring easier. Quote Link to post Share on other sites
RogerH Posted June 12, 2020 Report Share Posted June 12, 2020 (edited) Hi AndyM & R, keeping the earth wires (input / output )separate on the PWM works. See my circuit in my post above for the final layout. Hi Bob, I didn;t know about the MOSFET switching - many thanks. Roger Edited June 12, 2020 by RogerH Quote Link to post Share on other sites
AndyR100 Posted June 12, 2020 Author Report Share Posted June 12, 2020 3 hours ago, RogerH said: Hi AndyM & R, keeping the earth wires (input / output )on the PWM works. See my circuit in my post above for the final layout. Hi Roger, Excellent, many thanks for your persistence to find a solution and confirm that it will work happily wired that way. I'll look out for heater/headlamp/2-speed-wiper switch (are they all the same?) and then i'll be sorted as well. I have plumbed everything back in now, matrix is watertight, nice and toasty air coming out of the heater, with more fan-puff than before, doesn't take much to make me happy ...... Andy Quote Link to post Share on other sites
RogerH Posted June 12, 2020 Report Share Posted June 12, 2020 Hi Andy, any three position switch could do ity Here is one on ebay Switch Roger Quote Link to post Share on other sites
Andy Moltu Posted June 12, 2020 Report Share Posted June 12, 2020 I went for the real thing so I could use a proper knob on it. According to some of the TR suppliers these aren't available but I used them a couple of years ago when the wiper switch failed on mine & found them for Al Westbury who was told they were unavailable. https://www.ebay.co.uk/itm/222692850542?ssPageName=STRK:MESINDXX:IT&_trksid=p3984.m1436.l2649 I doubt I will fit the rebuilt heater tot he 4A until the winter when I'm planning to pull the engine apart and the gearbox tunnel will be out. (Not sure yhow easy it is to remove the heater with the tunnel in place) Quote Link to post Share on other sites
Lebro Posted June 12, 2020 Report Share Posted June 12, 2020 Ok, so I have opened up the controller shown below, https://www.ebay.co.uk/itm/12V-24V-Max-20A-PWM-DC-Motor-Stepless-Variable-Speed-Controller-9V-60V/353043539527?ssPageName=STRK%3AMEBIDX%3AIT&_trksid=p2060353.m2749.l2649 It uses 2 X mosfets to switch the -ve line, they are of a very good spec, being rated at 80 Amps, & having an on resistance (RDS on) of only 0.0037 ohms (so two in parallel would be 0.00185 ohms) the +ve input is directly connected to the +ve output, I have beefed up the wire gauges to drop the voltage loss even further. A warning for anyone using this type of controller - the metal case is not isolated from the circuit, & worse it is connected not to -ve in, but to the heatsink of a voltage regulator, on which the measured voltage is approx 8V, so the case must not touch the car body, or the controller will be destroyed. I have got around this by inserting an insulating "heatsink pad" between the case & the voltage regulator. The control potentiometer is 100K linear, I will probably change this for a physicaly larger one which I can fit the original rheostats knob onto. Bob. Quote Link to post Share on other sites
AndyR100 Posted June 12, 2020 Author Report Share Posted June 12, 2020 1 hour ago, Andy Moltu said: I doubt I will fit the rebuilt heater tot he 4A until the winter when I'm planning to pull the engine apart and the gearbox tunnel will be out. (Not sure yhow easy it is to remove the heater with the tunnel in place) I took mine out with the tunnel and dash untouched..... I did remove the radio and the glovebox - all came out in in about 2.5 - 3 hours including only mild cursing, fiddly but doable. ...... Andy Quote Link to post Share on other sites
AndyR100 Posted June 12, 2020 Author Report Share Posted June 12, 2020 2 hours ago, RogerH said: Hi Andy, any three position switch could do ity Here is one on ebay Switch Roger Thanks Roger ...... Andy Quote Link to post Share on other sites
AndyR100 Posted June 12, 2020 Author Report Share Posted June 12, 2020 1 hour ago, Lebro said: Ok, so I have opened up the controller shown below, https://www.ebay.co.uk/itm/12V-24V-Max-20A-PWM-DC-Motor-Stepless-Variable-Speed-Controller-9V-60V/353043539527?ssPageName=STRK%3AMEBIDX%3AIT&_trksid=p2060353.m2749.l2649 It uses 2 X mosfets to switch the -ve line, they are of a very good spec, being rated at 80 Amps, & having an on resistance (RDS on) of only 0.0037 ohms (so two in parallel would be 0.00185 ohms) the +ve input is directly connected to the +ve output, I have beefed up the wire gauges to drop the voltage loss even further. A warning for anyone using this type of controller - the metal case is not isolated from the circuit, & worse it is connected not to -ve in, but to the heatsink of a voltage regulator, on which the measured voltage is approx 8V, so the case must not touch the car body, or the controller will be destroyed. I have got around this by inserting an insulating "heatsink pad" between the case & the voltage regulator. The control potentiometer is 100K linear, I will probably change this for a physicaly larger one which I can fit the original rheostats knob onto. Bob. Great extra info Bob, many thanks for the warning and remedy for the casing as well ! ....... Andy Quote Link to post Share on other sites
RogerH Posted June 12, 2020 Report Share Posted June 12, 2020 1 hour ago, Andy Moltu said: I went for the real thing so I could use a proper knob on it. According to some of the TR suppliers these aren't available but I used them a couple of years ago when the wiper switch failed on mine & found them for Al Westbury who was told they were unavailable. https://www.ebay.co.uk/itm/222692850542?ssPageName=STRK:MESINDXX:IT&_trksid=p3984.m1436.l2649 I doubt I will fit the rebuilt heater tot he 4A until the winter when I'm planning to pull the engine apart and the gearbox tunnel will be out. (Not sure yhow easy it is to remove the heater with the tunnel in place) Hi AndyM, My GB and tunnel were out but they are not really the major hinderance. Remove the following - speedo & Tacho, the for/aft strut that attaches to the choke control on the 'H' frame.. Remove the righthand screen air vent piping. The glove box possibly could remain insitu. Roger Quote Link to post Share on other sites
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