ACTion P94 review

ACTion P94 review

JOHN ELSY builds this twin electronic speed controller and mixer unit

Diagram showing application of the P94 Unit

In all hobbies there are one or two areas where many of us fear to tread and in our model boating hobby, one of these is electronics. This can put a lot of us off from building and installing electronic kits, so to try and dispel these fears, here I will endeavour to boost your confidence. Anyone who is capable of producing a good soldered joint can extend their abilities and knowledge by completing one or two electronic self-assembly kits.

This kit is from ACTion R/C Electronics who have been around since 1994 building and selling electronic gizmos for the model boat market. Much of the range is available as kits as well as ‘ready to go’.

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Is there an advantage to building from an electronic kit? The kit price will be cheaper than a ready made version, plus there is the experience gained from assembling it. Self satisfaction has to be another bonus because nothing can beat that feeling of knowing you have added that little hidden extra to your model!

So, this is the P94 twin speed controller and mixer, all in one compact unit, length 74mm, width 50mm and height of 58mm (to the top of the heat sinks). There are currently two versions; the 20 amp P94 and the 10 amp P94 Lite version which does not need heat sinks so is only 30mm high, but otherwise is the same size. Photo 1 has the ACTion kit as supplied.

What do you get?

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In a large plastic bag you will receive six A4 sheets of instructions and some smaller bags containing: Power leads and hardware; resistors, capacitors and so forth; the four power transistors (that may have the heat sinks fitted) and two small transistors plus the main IC chip with a matching 14 pin socket in a dedicated anti-static bag.

There is also the plastic case and inside it you will find the printed circuit board and relays. Photo 2 is of all the components, but you are best advised to keep the transistors and i.c. chip in the anti-static bag until needed. Note also that in this picture the Power Mosfets are not fitted to their heat sinks. There is some variation in packing arrangements depending on the ACTion mood at the time!

Tools required

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Photo 3 gives an idea of what is required.

A 25 Watt soldering iron with a 3mm flat screwdriver tip will do the job but a 15 Watt soldering iron is a safer bet for the smaller components and better still would be a soldering station, but that’s not essential.

Flux cored solder, 22 SWG (0.711mm dia. is recommended).

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Small pair of wire side cutters.

Small long nosed pliers.

Spring locking tweezers.

Small flat blade screw driver.

A magnifying glass is handy.

A small crocodile clip as a heat shunt when soldering sensitive components.

Three or four small plastic containers for storing and keeping safe the individual components (small plastic sweet or food containers are ideal).

A multimeter is handy for testing, but is not essential.

Before starting

Before we start soldering there are a few golden rules!

1) Read the instructions!

2) Static electricity can harm some electrical components, so we must avoid this. Nylon clothing is a natural generator of static as are nylon carpets, so it is best to try and avoid this occurring.

3) A good level of light is essential and a desk lamp may help.

The instructions are laid out so that someone with little knowledge of electrical components will easily understand them as each component is described in complete detail, so once thoroughly familiarised, we can begin.

First step

A great help to the assembly is to sort out the components into the plastic trays, Photo 4. If you are not used to handling static sensitive components then leave the transistors and IC chip in their protective plastic bag until they are needed. The printed circuit board has the solder track on one side and the reverse component side is plain. There are no reference marks for the positioning of the components on this plain side. What we can easily do is to offer the printed circuit board (pcb) against the component layout diagram in the instruction sheets and determine a reference point from which to begin. This will also ensure the board is the correct way around, Photo 5, where you will see that I have ‘arrowed’ one hole. This is where the main negative power cable is soldered and thus confirms the positions of the rest of the components with the aid of the layout diagram.

Now, following the instructions, fit the resistors R2 to R8. Resistors are the most heat tolerant of the electrical components and can normally be fitted either way around. On the body of the resistor there are colour bands. The purpose of these is to reveal the value of the resistor. The colour bands are read from left to right and there will be one band spaced a bit away from the others. This is the tolerance band and is usually either silver or gold in colour. As an example of the preciseness of the instructions: ‘R2 and R3 are 100R 1/4 Watt resistors, brown/black/brown’. This makes identification idiot proof.

Here in Photo 6, you can see how a resistor is fitted prior to soldering. On the track side of the circuit board, bend the wire legs of the component slightly apart to stop it falling out when the board is turned over to solder it in place. A useful tip is to solder just one component at a time, but before you cut the excess leads off, double check it is in the right place by comparison with the component layout diagram. Photo 7 has all seven resistors fitted, plus the wire link on the bottom right corner.

In the instructions, the next step is to determine the correct position and then fit the 14 pin socket for the microprocessor chip. For ease and clarity of photographs I left this socket out of the assembly at this stage, but that shouldn’t stop you following the instructions to a ‘T’. Please note that the socket has a notch at one end. This is to indicate which way the chip will fit into it and this notch must face the right way on the board, but all is not lost if you solder it the wrong way around. If this happens, don’t try and unsolder it unless you have the proper tools, but leave it in position and mark the correct end with a permanent felt tip pen.

The important thing to watch for when soldering the socket in place is not to bridge the pins with solder as the pins are very close together. So please double check this component once fitted and soldered.

Fitting the capacitors

In this kit there are two types; monolithic and electrolytic, and the total number of capacitors in the unit are three.

There are two monolithic and these are a bit like resistors in that they can be fitted either way around and are not too heat sensitive, but prolonged heat will destroy them. These are light blue in the photographs.

There is one electrolytic and this is the first component that MUST be fitted to the board the right way around.

The shape of the electrolytic capacitor in this kit resembles a tin can with two wire legs sticking out of the bottom, one long and one short. The short leg is the negative. Next to that short leg on the capacitor body there is a vertical stripe which has a negative marking on it which also helps to identify the negative side of the component.

To help fit the electrolytic capacitor correctly, locate the holes in the circuit board and then using the component layout diagram as a reference guide, mark the negative hole with a felt tip pen. Photo 8 has the three capacitors fitted, the two light blue components being the monolithic capacitators.

Fitting the two diodes

Diodes can come in all shapes and sizes, but the ones in this kit are cylindrical with a thick wire at each end. They are black in colour with a silver band round one end and this is the positive side. They must be fitted the correct way around, just like the electrolytic capacitor. These diodes are soldered in place vertically on the board and the silver band is uppermost. Photo 9 has them together at the right hand end of the board.

Fitting the two header pins

These are for the rudder servo plug and also a third speed controller, Do ensure that the short ends of the pins and NOT the long ends are soldered into the circuit board, Photo 10.

Time to fit some of the sensitive parts

Mosfet transistors:

These are static and heat sensitive components and must be handled with some care. The instructions supplied suggest in depth a method of discharging any static using an old tin lid or aluminum cooking foil. In this construction project the sensitive parts were placed in the metal lid of an empty sweet tin with the tip of the hot soldering iron placed on to the far edge of it and well away from the components. Place you free hand on the opposite edge of the tin away from the soldering iron and any static will now discharge to earth (or if you are extremely unlucky and the soldering iron wiring is faulty, you may get a direct connection to the National Grid, so be careful with all electrical tools! – Editor).

Mosfet transistors must be fitted the right way and the flat face on the body of the component is to face towards the diodes that have already been fitted. For those that are new to electronics it is recommended that a heat shunt is used to prevent too much heat from the soldering iron being transferred to the component when making the joint; spring tweezers or crocodile clips make good heat shunts. Do not try and push the transistors all the way down on to the circuit board they are mounted with about 6mm clearance, please see Photos 11 and 12.

DIL switch and variable resistor

These are fitted next. The point to watch, is to fit the DIL switch the right way around with the numbers on the top of the switch to the left. Following on from this, the variable resistor (or pot) is next. The legs of this component are a little tight in the locating holes and you need to gently rock the pot from side to side with a little downward pressure to push it home. Photo 13 has the DIL switch and variable resistor in place, bottom left of the pc board in this picture.

14 pin IC socket

I now fitted this the with the aid of a pair of spring tweezers to hold it level and in place when soldering, Photo 14.

Power Mosfets

The four of these are next to be fitted, not forgetting to follow the static discharge routine. The heat sinks now come factory fitted to them and this makes the task even easier. The Power Mosfets are located along the long edges of the circuit board. Check they are facing the right way then clip on a heat shunt just to be on the safe side, but with this in place it can be a bit awkward to hold the component in place and solder at the same time, so care must be taken, Photo 15.

Before the next components are fitted it is a good idea to check that there are no splashes of solder or badly made joints on the track side of the board, as it is a lot easier to put right now rather than later.

Relays

The two side by side relays are next to be fitted and they only go in one way. The use of spring tweezers helps to keep them flat against the pc board whilst they are being soldered, Photo 16.

Terminal blocks

The last two components to be fitted are the terminal blocks, Photo 17.

Power cables

If a 15 Watt soldering iron has been used throughout the assembly, it will not have the heat to solder the 14 swg silicone power supply cables. The trick to getting the tinned end of the cable through the hole in the circuit board is to twist the bare strands tightly, then tin with a 25 Watt soldering iron and once cool, dress the tinned end with a file so that it is a nice fit through the hole. Once the four power cables are fitted, Photo 18, the next step is to reinforce the copper track between the positive (+ve) lead inputs and where the track divides to feed both relays with a piece of 15 amp single strand copper wire, Photo 19.

The last bit of soldering

Fitting the r/c feed cables and plugs

When ordering the kit, specify the type of radio receiver you will be using. This is because ACTion will pre-fit the plugs to the cables. So before you attach the leads don’t forget to fit the little plastic identification collars. One is marked S (steering) the other T (throttle) and please ensure that the cables are in the right order. White is signal, Red is positive power and Black is negative power, Photo 20.

Cleaning up

The track side of the board now has to be cleaned which can be done with a tooth brush and some spirit cleaner. Methylated spirits is good but even better is Isopropyl. Following cleaning and double checking of the solder joints, the 14 pin IC was fitted.

Now clean the work area so that you do not put the unit down on top of offcuts of wire by accident and thus short it out when it is powered up!

Testing and set-up

Set the two-way DIL switch for Mode 4 as per the instructions.

Plug the leads marked T and S in to the throttle (T) and rudder (S = steering) channels of a suitable receiver and then switch on the matching transmitter. Now switch on the receiver power supply, move the throttle stick from neutral to full forward and then full reverse and as you do this, listen for the relays ‘clicking’.

If you hear this sound then it proves that this part of assembly is okay.

Next plug in a spare servo to H1, the rudder connection on the board, then move the rudder stick on the transmitter from left to far right to operate the rudder servo which should function and as it moves, so the relays should operate. This proves that the mixer part of the circuit is functioning correctly.

Disconnect the unit from the receiver and connect two suitable motors to the motor output terminals TB1 and TB2, then reconnect leads T and S to the receiver. So far, so good!

The main power battery should now be connected to the pc board. Pay particular attention to this as the two main red wires are connected together at the positive terminal on the battery and the black wires are connected together at the negative terminal. Set the throttle stick to neutral, switch on the transmitter and then the receiver, and slowly move the throttle stick forward. The motors should work. Now move the rudder stick either to the left or right of centre and one motor will slow down and the other will speed up. So, no complicated multi-meters are needed! If you have soldered correctly, then it will work and that is all the kit builder really needs to know. Photo 21 has everything laid out for bench testing.

The case

This has to have holes cut in it, and that is the situation even if you purchase an assembled unit.

All the dimensions are in the instructions and the usual method is to mark them on to the case. One alternative is to photocopy the case cutting diagrams from the instructions, cut them out and attach to the case with PVA glue and use as direct templates. Then cut the holes out, clean the burrs off the edges and remove the templates with warm water. Dry the case thoroughly and fit the unit inside it, Photo 22.

Conclusion

Photo 23 is of the finished unit, fully wired and fitted into a model boat. I hope that readers who may not be familiar with electronics have been given some encouragement. For those with experience, I have deliberately left out all of the descriptions and calculations of the components involved in the kit. The ACTion R/C Electronics P94 instructions are foolproof, but the manufacturer does offer a ‘fix it’ service, however you do not need an in depth knowledge of electronics to build this kit. ACTion R/C Electronics attend many UK model shows and advertise regularly in this magazine and their address is: 19 Carisbrooke Drive, Nottingham, NG3 5DS, England, tel: 01159 607951,
website: www.action-electronics.co.uk.

The P94 20 amp unit is priced at £78 assembled (£75 for the 10 amp ‘Lite’ version), but it is 15% less when supplied in kit form.

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